Chapter 7: the Nervous System - PowerPoint Presentation

Slide1

Chapter 7: the Nervous System

Bio 24Slide2

Organization of the nervous systemSlide3

Organization of the nervous system

Our responses to stimuli may be voluntary or involuntary or both

Example: in response to low blood pressure, you may contract smooth muscles to decrease the diameter of your blood vessels, AND feel thirsty, causing you to take a drinkSlide4

Central and peripheral nervous systems

Your

central nervous system (CNS)

consists of your brain & spinal cord

Your

peripheral nervous system (PNS)

consists of all the nerves that carry information to and from your CNSSlide5

structure of nervous tissueSlide6

Cells of the nervous system

There are two main types of cells in the nervous system:

Neurons

: communicate with other cells using electrical and chemical signals

Neuroglia

: support and insulate the neurons; FAR more abundant than neuronsSlide7

Parts of a neuron

Cell body

Dendrites

: receive signals from other neurons

Axons:

send signals to other cells

Schwann cells (

neuroglial

cells) wrap around the axons to form

myelinSlide8

Schwann cells form myelin in the PNS

Schwann cells form myelin by wrapping around PNS neurons

Oligodendrocytes

form myelin by wrapping around CNS neurons

“White matter” is nerve tissue wrapped in myelin (axons), “gray matter” is

unmyelinated

(usually cell bodies)Slide9

Multiple sclerosis

Autoimmune disease that attacks myelin in both the CNS & PNS

Multiple functions of the nervous system may be impairedSlide10

Many types of sensory receptors

In response to physical stimulation, sensory receptor cells create electrical signals that travel to the central nervous system

S

pecialized senses (hearing, sight, smell & taste) have special receptor cells to be discussed in chapter 8Slide11

Electrical signals generated by neurons are action potentials

Electrical energy is the result of movement of ions

When neurons generate action potentials it involves ions moving across the cell’s plasma membrane

An

action potential

is an electrical signal that starts in a neuron and travels down the axonSlide12

The synapse

When electrical signals reach the end of axons, they trigger the release of chemicals from the

axon terminal

The space between the axon terminal and another cell is called the

synaptic cleft

and the connection between the two is called the

synapseSlide13

Neurotransmitters are released at the synapse

Neurotransmitters are chemical signals released from a neuron’s axon terminal onto a target cell

The target cell may be a neuron, too, or another cell type

Many recreational and therapeutic drugs work by influencing the action of neurotransmittersSlide14

Reflexes

A

reflex

is an automatic response to a stimulus

Reflexes can control either skeletal muscles (

somatic reflexes

) or involuntary muscles (

autonomic reflexes

)

Reflexes are integrated by your spinal cord NOT your brain, hence they are not conscious actionsSlide15

the central nervous systemSlide16

4 major regions of the brain

Brain stem

: controls breathing and blood pressure; many nerves pass through

Cerebellum

: controls movement

Diencephalon

: integrates sensory information & mediates emotional response

Cerebrum

: controls all “higher thought”Slide17

Areas of the cerebrum are specialized for different functionsSlide18

The cerebral cortex receives sensory information and sends motor informationSlide19

The corpus callosum connects the hemispheresSlide20

protection of the cnsSlide21

The CNS is vulnerable to damage

Cells of the central nervous system have a very limited ability to regenerate themselves

The cells themselves are soft and easily damaged (your brain has the consistency of tofu)

The

blood-brain barrier

refers to the fact that capillaries in the brain are less permeable than those in other parts of the body; this helps protect your brain from damage due to chemicals in your bloodstreamSlide22

Bones and meninges protect the CNS

The meninges consist of the:

dura

mater

arachnoid mater

pia

mater

layers of connective tissue membrane that protect the brain and spinal cord

Meningitis

is inflammation of the meninges caused by viral or bacterial infection; can be serious or fatal!Slide23

Cerebrospinal fluid in and around the brain and spinal cord also protects itSlide24

Hydrocephalus is caused by an overabundance of CSFSlide25

brain dysfunctionSlide26

Traumatic brain injuries

Most often caused by car accidents

Concussion

: a mild traumatic brain injury; may result in temporary loss of consciousness

Intracranial hemorrhage

: bleeding in the brain; can damage brain tissue

Cerebral edema

: swelling of the brain; sometimes part of the skull is temporarily removed to treat thisSlide27

Stroke

Stroke

is the result of a blood clot that blocks blood flow to part of the brain; if brain tissue is deprived of blood for even a few minutes, it dies

Aphasia

, or reduced ability to produce or understand language, is common after stroke affecting the left hemisphereSlide28

the spinal cord & peripheral nervous systemSlide29

The spinal cord

Spinal nerves

carry information both to and from the CNS

The nerves then split and the sensory information goes in through a structure called the

dorsal root

; motor information goes out through the

ventral root Slide30

The spinal cord

Dorsal horns

(gray matter) contain interneurons that connect neurons to each other

White matter of the spinal cord is

myelinated

axons carrying info up and downSlide31

Organization of the nervous systemSlide32

The sympathetic and parasympathetic divisions

Sympathetic nervous system

is activated under “fight or flight conditions”

Blood flow to muscles increases

Pupils of eyes dilate

Digestion is inhibited

Heart rate increases

Parasympathetic nervous system

is activated under “rest and digest” conditions

Table 7.3 in your book lists several specific effects each

of these has!