PHYSIOLOGY OF THE NERVOUS SYSTEM - PowerPoint Presentation

Slide1

PHYSIOLOGY OF THE

NERVOUS SYSTEM

Sept 20, 2011

Group 4

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Physiology of the Nervous System

Functions and Divisions

Nervous Tissue

Neurons and

neuroglia

Types

Nerve signal and transmission

Central Nervous System

Brain and spinal cord

Peripheral Nervous System

Types of nerves

Somatic Motor Nervous System

Autonomic Motor Nervous System

Diseases

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Functions

Sensory Input

- sensory receptors in the skin and organs generate nerve signals

2. Integration

- brain and spinal cord interpret the data and signal nerve responses

Motor Output

- nerve impulses from the brain and spinal cord go to the effectors

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Divisions

Central Nervous System (CNS)

- lie midline of the body

- brain and spinal cord

Peripheral Nervous System (PNS)

- project out from the CNS

- cranial and spinal nerves

1. afferent/ sensory

2. efferent/ motor

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CNS

PNS

Brain

Spinal cord

Sensory Nerves

(afferent)

Motor Nerves

(efferent)

Somatic Sensory Nerves

Autonomic Motor Nerves

Somatic Motor Nerves

Visceral Sensory Nerves

Parasympathetic

Sympathetic

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Nervous Tissue

Neurons

Dendrite

- receives signals from receptors

Cell Body-

contain nucleus and most of the cytoplasm

Axon

- conducts nerve impulses

Fibers

- long axons

Nerves-

fibers outside the brain and spinal cord

Tracts

- fibers in the brain and spinal cord

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Nervous Tissue

Types of Neurons

Motor Neurons

- (

multipolar

) take nerve impulses from the CNS to muscles, organs or glands

Sensory Neurons

- (

unipolar

) take nerve impulses from sensory receptors to the CNS

Interneurons

/ Association neurons

- (

multipolar

) convey nerve impulses between various parts of the CNS

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A Typical Nerve Cell/ Neuron

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Types of Neurons

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Nervous Tissue

B.

Neuroglia

-

nourish the neurons

In the brain:

1.

microglia

- engulf bacterial and cellular debris

2.

astrocytes

- provide nutrients and produce a hormone

3.

oligodendrocytes

- form myelin

4.

ependymal

cells

- form cerebrospinal fluid

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Nervous Tissue

Outside the brain:

Schwann Cells/

neurolemmocytes

-

provide myelin sheath to nerve fibers

Nodes of

Ranvier

/

neurofibril

nodes-

gaps between Schwann cells

Myelin sheath-

speeds up conduction

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A

Neuroglia

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Nerve Signal Conduction

Neurons- transmit

nerve signals

Nerve Signal-

action potential, conducted by the axon

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Nerve Signal Conduction

Resting Potential

nerve cell has -70 mV of stored energy

exists because cell membrane is polarized

necessary for efficient work

Maintained through the sodium-potassium pump

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Resting Potential

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Nerve Signal Conduction

Action Potential

Process of conduction that occurs in the axons

Begins with a

stimulus

Depolarization - protein channels for Na

+

open

Repolarization

- protein channels for Na

+

close and channels for K

+

open

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Action Potential

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Action Potential

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Conduction of Action Potentials

Unmyelinated

Axons

Action potential at one local stimulates an adjacent part of the axon membrane to produce an action potential

Slow, 1m/sec in thin axons because each section of the axon must be stimulated

Myelinated

Axons

Action potential at one node of

Ranvier

causes an action potential at the next node

(

saltatory

conduction

)

Faster, 100m/sec in thick axons

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Conduction of Action Potentials

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Refractory Period

occurs soon as the action potential has passed by each successive portion of the axon

Axon is unable to conduct an action potential

Ensures one-way direction of an impulse

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Transmission Across a Synapse

Axon terminal

- swelling at the tip of the axon

Synapse

– region of close proximity between the axon terminal of a neuron and a dendrite or cell body of another neuron

Presynaptic

membrane

- membrane of the first neuron

Postsynaptic membrane

- membrane of the next neuron

Synaptic cleft-

small gap between the two membranes

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Transmission Across a Synapse

Neurotransmitters

Carry out transmission across a synapse

stored in synaptic vesicles in the axon terminals

e.g. Ach and NE

Excitatory neurotransmitter

Inhibitory neurotransmitter

graded potential

small signals from a synapse

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Transmission Across a Synapse

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Transmission Across a Synapse

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Central Nervous System

Consists of the brain and spinal cord

Composed of:

Gray mater-

contains cell bodies and short,

nonmyelinated

axons

White mater-

contains

myelinated

axons that run together in tracts

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Central Nervous System

Meninges

(sing.

Meninx

)-

protective membranes of the spinal cord and brain

Dura mater

- outer

meninx

; tough, white, fibrous connective tissue that lies next to the skull and vertebrae

Arachnoid

mater

- “spider-like”; consists of spider web like connective tissue

Pia

mater

- deepest

meninx

; very thin and closely follows the contours of the brain and spinal cord

Slide30

Central Nervous System

Subarachnoid space

space in between

arachnoid

and

pia

mater

Contains

cerebrospinal fluid

similar to the plasma that forms a protective cushion around and within the CNS

Fills ventricles and hollow ventral canal of the spinal cord

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Spinal Cord

Long, thin tubular bundle of Nervous System.

Found inside the vertebra.

Supports cells that extends the brain.

Begins at the occipital bone.

Main pathway for information connecting the brain and peripheral nervous system.

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Layers of Spinal Cord (

Meninges)

Dura MateArchnoid MaterPia Mater

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The subarachnoid space is the space which normally exists between the

arachnoid

and the

pia

mater, which is filled with cerebrospinal fluid. Normally, the

dura

mater attached to the skull, or to the bones of the vertebral canal in the spinal cord. The

arachnoid

is attached to the

dura

mater, while the

pia

mater is attached to the central nervous system tissue. When the

dura

mater and the

arachnoid

separate through injury or illness, the space between them is the subdural space.

Slide34

Spinal Cord Level Numbering System

The spinal nerves carry information to and from different levels (segments) in the spinal cord. Both the nerves and the segments in the spinal cord are numbered in a similar way to the vertebrae. The point at which the spinal cord ends is called the

conus

medullaris

, and is the terminal end of the spinal cord. It occurs near lumbar nerves L1 and L2. After the spinal cord terminates, the spinal nerves continue as a bundle of nerves called the

cauda

equina

. The upper end of the

conus

medullaris

is usually not well defined.

Slide35

There are 31 pairs of spinal nerves which branch off from the spinal cord. In the cervical region of the spinal cord, the spinal nerves exit above the vertebrae. A change occurs with the C7 vertebra however, where the C8 spinal nerve exits the vertebra below the C7 vertebra. Therefore, there is an 8th cervical spinal nerve even though there is no 8th cervical vertebra. From the 1st thoracic vertebra downwards, all spinal nerves exit below their equivalent numbered vertebrae.

The spinal nerves which leave the spinal cord are numbered according to the vertebra at which they exit the spinal column. So, the spinal nerve T4, exits the spinal column through the foramen in the 4th thoracic vertebra. The spinal nerve L5 leaves the spinal cord from the conus medullaris, and travels along the cauda equina until it exits the 5th lumbar vertebra.

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1

Spinal Nerve

5

Central Canal

2

Dorsal Root Ganglion

6

Grey Matter

3

Dorsal Root (Sensory)

7

White Matter

4

Ventral Root (Motor)

 

 

Slide38

Brain

Overview on the parts of the brain

Forebrain

Telencephalon

Cerebrum

Cerebral Cortex

Frontal lobe

Parietal lobe

Temporal lobe

Occipital lobe

insula

Brocas

area

Corpus

callosum

Basal Ganglia

The Limbic System

Diencephalon

Thalamus

Hypothalamus

Midbrain

Tectum

Tegmentum

Hind brain

Cerebellum

Pons

Medulla oblongata

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Forebrain

Cerebrum

Largest portion of the brain

Last center to receive sensory input

Carry out integration before commanding voluntary motor responses

Carries out higher thought of processes required for learning and memory and for language and speech

Compose of 2 hemispheres

Left and right cerebral hemisphere

Frontal lobe- reasoning and movement

Parietal lobe- somatic sensing includes taste

Temporal- hearing

Occipital- vision

Brocas

area- found only in left cerebral hemisphere; motor speech area

Slide40

Cerebral cortex

-thin but

convulated

outer layer of gray matter which covers the cerebral hemisphere

-accounts for sensation, Voluntary movement, and all thought processes we associate with consciousness

Limbic system

 

hippocampus

 (sea horse)

 

and the 

amygdala

 (almond), along with portions of the hypothalamus, thalamus, caudate nuclei, and septum function together

function:

Causes the subject to experience pain, rage, pleasure or sorrow

Corpus

callosum

white matter connects the cerebral hemisphere

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Diencephalon

Hypothalamus

- forms the floor of the 3

rd

ventricle

Maintains homeostasis by regulating hunger, sleep, thirst, body temperature and water balance.

Also controls the endocrine system and autonomic nervous system

Thalamus

- consists of 2 masses of gray matter located in the sides and roof of the 3

rd

ventricle

-

- integrates visual, auditory and

somatosensory

information and sends it to appropriate portions of the cerebrum

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Mesencephalon

Tectum

- include the 

superior

colliculi

 and

the

inferior

colliculi

- visual reflexes and reaction to moving stimuli

Tegmentum

- reticular formation,

periaqueductal

gray matter, and the red nucleus and

substantia

nigra

receives sensory information and is involved with attention, sleep and arousal, muscle tonus, movement, and various vital reflexes

Slide43

Hind brain

Cerebellum- separated from the brain stem by 4

th

ventricle

Receives sensory input from eyes, ears, joints and muscles

Receives motor output from cerebral cortex where this part should be located

Maintains posture and balance

Ensures that the muscles work together for smooth and coordinated movements

Slide44

Pons -

 large bulge in the brain stem between the

mesencephalon

and the medulla oblongata

 believed important in the role of sleep and arousal

Medulla oblongata-

origin of the reticular formation and consists of nuclei 

control center for cardiac, vasoconstrictor, and respiratory functions. 

Reflex activities, including vomiting, are controlled by this structure of the hindbrain

Slide45

Peripheral Nervous System

Composed of:

Nerves

- bundles of axons

Ganglia

- swellings associated with nerves that contain collections of cells bodies

Slide46

Peripheral Nervous System

Subdivisions:

A

fferent/ sensory system

Somatic sensory system-

serves the skin, skeletal muscles, joints and tendons; special senses

Visceral sensory system-

supplies internal organs

Efferent/ motor system

Somatic motor system-

carries commands away from the CNS to the skeletal muscles

Autonomic motor system-

regulates activity of cardiac and smooth muscles and glands

Slide47

Types of Nerves

Cranial Nerves

12 pairs, concerned with the head, neck and facial regions of the body

Motor nerves-

with only motor fibers

Sensory nerves-

with only sensory fibers

Mixed nerves-

with both motor and sensory nerves

Slide48

Table, fig 8.11

Nerve

Type

Transmits Nerve Impulses to (Motor) or from (Sensory)

Olfactory (I)

Sensory

Olfactory receptors for sense of smell

Optic (II)

Sensory

Retina for sense of sight

Oculomotor

(III)

Motor

Eye muscles (including eyelids and lens);

pupil (parasympathetic region)

Trochlear

(IV)

Motor

Eye muscles

Trigeminal (V)

Mixed

Teeth, eyes,

skin, and tongue

Jaw muscles (chewing)

Slide49

Abducens

(VI)

Motor

Eye muscles

Facial (VII)

Mixed

Taste buds of anterior tongue

Facial muscles

( facial expression) and glands (tear and salivary)

Vestibucochlear

(VIII)

Sensory

Inner ear for sense of balance and hearing

Glossopharyngeal

(IX)

Mixed

Pharynx

Pharyngeal muscles (swallowing) salivary

glands

Slide50

Vagus

(X)

Mixed

Internal organs, external ear canal, eardrum, back of throat

Internal organs (parasympathetic division), throat muscles (somatic motor division)

Spinal Accessory

(XI)

Motor

Neck and back muscles

Hypoglossal (XII)

motor

Tongue muscles

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Slide52

Types of Nerves

B. Spinal Nerves

- 31 pairs, one of each pair is on either side of the spinal cord

- grouped depending on the location on the vertebral column

-

cervical

-

thoracic

-

lumbar

-

sacral

Slide53

Table fig 8.12

Name

Spinal Nerves Involved

Function

Musculocutaneous

nerves

C5-T1

Supply muscles of the arms of the anterior sides, and skin of the forearms

Radial nerves

C5-T1

Supply

muscles of the arms on the posterior sides, and skin of the forearms and hands

Median nerves

C5-T1

Supply muscles of the forearms, and muscles and

skin of the hands

Ulnar

nerves

C5-T1

Supply

muscles of the forearms and hands, and skin of the hands

Slide54

Phrenic

nerves

C3-C5

Supply

the diaphragm

Intercostal

nerves

T2-T12

Supply

intercostal

muscles, abdominal muscles, and skin of the trunk

Femoral

nerves

L2-L4

Supply muscles and skin of the anterior thighs and legs

Sciatic nerves

L4-S3

Supply muscles and skin of the posterior thighs, legs, and feet

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Slide56

Somatic Motor Nervous System

Mostly voluntary actions

Other action are due to

reflexes

Automatic involuntary responses to changes occurring in or outside the body

Occurs quickly

Protective mechanisms essential to homeostasis

Spinal reflex

Cranial reflex

Slide57

Slide58

Slide59

Somatic Motor System

Some reflex used to determine if nervous system is reacting properly:

Knee-jerk reflex

Ankle-jerk reflex

Slide60

Autonomic Motor Nervous System

Sympathetic

“fight or flight”

Important during emergency situations

Accelerates heart beat and dilates bronchi

Inhibits digestive tract (digestion is not an immediate necessity during emergencies)

Neurotransmitter: NE

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Slide62

Autonomic Motor Nervous System

B. Parasympathetic

“

rest and digest”/ housekeeper division

Promotes all of the internal responses we associate with a relaxed state

Ex: contraction of the pupil of the eyes, promote digestion, slow heart rate, lower strength of cardiac contraction

Neurotransmitter:

ACh

Slide63

Slide64

Slide65

Diseases of the Nervous System

Slide66

Term

Definition

Cause

Effect

Bell's Palsy

A form of Neuritis that involves paralysis of the facial nerve causing weakness of the muscles of one side of the face and an inability to close the eye.

Unknown.

Paralysis of the facial nerve;

weakness of the muscles of one side of the face;

may result in inability to close the eye.

Cerebral

Palsy

A

nonprogressive

disorder of movement resulting from damage to the brain before, during, or immediately after birth.

Cerebal

Palsy is attributed to damage to the brain, generally

occuring

before, during, or immediately after birth.

It is often associated with other neurological and mental problems

. There

are many causes including birth

injury,

hypoglycaemia

,

and

infection.

The most common disability is a spastic paralysis.

Sensation is often affected, leading to a lack of balance, and intelligence, posture and speech are frequently impaired. Contractures of the limbs may cause fixed abnormalities.

Other associated features include epilepsy, visual

impairment,

reduced hearing, and

behavioural

problems.

Slide67

Term

Definition

Cause

Effect

Parkinson's Disease

Degenerative disease process (associated with aging) that affects the basal ganglia of the brain.

Associated with a deficiency of the neurotransmitter dopamine.

Also associated with aging.

The

commonest symptom is tremor, which often affects one hand, spreading first to the leg on the same side then to the other limbs. It is most profound in resting limbs, interfering with such actions as holding a cup.

Multiple Sclerosis

A chronic disease of the nervous system that can affect young and middle-aged adults.

The course of this illness usually involves recurrent relapses followed by remissions, but some patients experience a chronic progressive course.

The myelin sheaths surrounding nerves in the brain and spinal cord are damaged, which affects the function of the nerves involved.

The underlying cause of the nerve damage remains unknown.

Multiple

Scerosis

affects different parts of the brain and spinal cord, resulting in typically scattered symptoms. Unsteady gait and shaky movement of the limbs, rapid involuntary movements of the eyes, and defects in speech pronunciation.

Slide68

Amnesia

is a state of mind wherein months or years of memories suddenly vanish.  There are two types of amnesia:  organic and functional. 

Organic amnesia

is caused by damage to the brain brought about by head injuries, severe illness, senility (old age), concussions or violent blows, alcoholism, and stroke. 

Functional amnesia

is caused by trauma (shocking event or horrifying scene) or stress.  Generally, organic amnesia lasts longer than functional amnesia.

Alzheimer disease

is the most common cause of dementia. It affects more women than men, and the clinical course generally lasts approximately five years.  The younger the individual is at the onset of the disease, the more severe the deficits for the patient.  One famous contemporary who suffers from the disease is former U.S. President Ronald Reagan.

Stroke

is a general term for a sudden neurological event which results in the new onset of neurological symptoms.

Stroke Animation Video.flv