Ch 8

Functions of the nervous system

Neurons are excitable cells because their plasma membrane is polar, receives sensory information, neurons integrate information, and control all cells in the body

Function of Dendrites

receive incoming signals from other neurons

Function of soma

Cell body, contains the cell nucleus and much of the chemical machinery common to most cells (soma is Greek for "body").

Function of axon hillock

To help determine if the action potential is strong enough to send

Function of axon

carries nerve impulses away from the cell body

Function of synaptic end bulb

Swelling at end of axon, in which neurotransmitter is synthesised

Function of nucleus

Control center of the cell

Function of ganglion

swelling that contains cell bodies of sensory neurons

Function of tract of nervous system

tracts are bundles of nerve fibers that transmit information. They act as highways within the central nervous system, carrying signals between different parts of the brain and spinal cord, or between the brain and the periphery.

Function of the nerve

send and receives messages

Function of neuron

process and transmit information

function of neuroglia

Most abundant in nervous system and protect neurons and aid in their function

Neuroglia cells include

Oligodendrocytes, astrocytes, ependymal cells, and microglia.

Oligondendrocytes

a) Found in the CNS,

b) Form myelin in brain and

spinal cord

Astrocytes (Star-like cell)

a) Found in the CNS,

b) Protoplasmic: Cover

brain surfaces, from

blood-brain-barrier,

remove K+ and

neurotransmitters from

extracellular fluid, (ECF)

& regulate its

composition.

c) Fibrous: Form

supportive framework in

CNS, form scar tissue

after injury

Ependymal cells

a) Found in CNS,

b) Line cavities of brain and

spinal cord,

c) Secrete and circulate

cerebrospinal fluid.

Microglia cells

a) Found in CNS,

b) Developmentally not

related to nervous tissue,

but to immune tissue,

c) Phagocytize and destroy

microorganisms, foreign

matter, and dead nervous

tissue.

Describe neuroglia in PNS

Schwann cells: Found in PNS, form neurilemma around

all PNS fibers,

• Myelin sheath around most PNS axons,

• Form 'naked' regions called 'Nodes of Ranvier'

• Aid in regeneration of damaged nerve fibers.

Describe electrical synapse

Connected by channel proteins called gap junctions to allow ionic current to flow passively from one neuron to another. Transmission can be bidirectional

• Transmission is very fast

• Plays important role in

synchronizing the electrical

activity of a group of neurons

Describe chemical synapse

• Synaptic vesicles from presynaptic

neurons release into the synaptic

cleft neurotransmitters that bind to

receptor proteins on the

postsynaptic neuron.

• Transmission is unidirectional.

• Transmission is slower than

electrical synapses.

• Neurotransmitters are removed

from the synaptic cleft to terminate

signaling and free postsynaptic

neurons for signaling event.

ionotropic receptors

a channel that opens when the neurotransmitter binds to it. message' to postsynaptic cell results in 'ions' moving

through receptor (similar to neuromuscular junction)

• ions such as Na+ to depolarize or K+ to hyperpolarize

the postsynaptic neuron.

metabotropic receptors

receptors that are associated with signal proteins and G proteins. results in activation of other enzymes (proteins),

• and activation of a 2nd messenger system

Describe Catecholamines

effects depend on postsynaptic

receptor,

• Norepinephrine (noradrenalin):

• Involved in dreaming, awake states,

• Can excite cardiac muscle can excite or inhibit smooth muscle.

• Epinephrine (adrenaline):

• Involved in excitation of cardiac muscle, and excitation or

inhibition of smooth muscle

Describe dopamine

Involved in elevation of mood and control of skeletal

muscle (missing - results in Parkinson's disease)

Describe serotonin

Involved in sleepiness, alertness, thermoregulation and

mood.

• Many mood-altering medications (for clinical depression)

work to prevent serotonin uptake (serotonin-uptake

inhibitors)

Describe histamines

Secreted from hypothalamus as neurotransmitter and

many tissue in response to injury

• Potent vasodilator in nervous system and other tissues.

What are baroreceptors, and where are they located?

Baroreceptors are stretch receptors located in the carotid artery that detect increased arterial diameter, especially during hypertension.

What do baroreceptors detect?

They detect changes in blood pressure.

Are baroreceptors more sensitive to hypertension or hypotension?

They are more sensitive to hypertension.

Which nerve carries afferent signals from the baroreceptors?

The glossopharyngeal nerve (cranial nerve IX).

Where does the afferent signal from baroreceptors go in the brain?

To nuclei in the pons and medulla.

What is the path of the efferent signal after synapsing in the brainstem?

Interneurons synapse on the vagus nerve (cranial nerve X), which is parasympathetic.

What does the vagus nerve do in response to high blood pressure detected by baroreceptors?

It synapses on the terminal ganglion of the heart, and the postsynaptic neuron releases ACh to decrease heart rate.