Ch 4 The Nervous System

Question 1

Astrocytes

Answer 1

Nourish neurons and form blood-brain barrier which controls the transmission of solutes from the bloodstream to the nervous tissue

Question 2

Ependymal cells

Answer 2

Line the ventricles of the brain and produce cerebrospinal fluid which physically supports the brain and serves as a shock absorber

Question 3

Microglia

Answer 3

Phygocytic cells that ingest and break down waste products and pathogens in the CNS

Question 4

Oligodendrocytes

And Schwann cells

Answer 4

Oligodendrocytes in CNS

and Schwann cells in PNS produce myelin around the axons

Question 5

Soma

Answer 5

Cell body of neurons

Question 6

Dendrites

Answer 6

Receive incoming messages from other cells

Question 7

Axon hillock

Answer 7

Integrates incoming signals
Next step down from soma
Plays an important role in action potentials or the transmission of electrical impulses down the axon

Question 8

Axon

Answer 8

Next step after axon hillock Long appendage that terminates in close proximity to a target structure.

Question 9

Myelin

Answer 9

Most axons are covered in this to prevent signal loss or crossing of signals

Question 10

Myelin sheath

Answer 10

Insulation for the axon

Increases the speed of conduction in the axon

Question 11

Nodes of Ranvier

Answer 11

Critical for rapid conduction

Small breaks in the myelin sheath

Question 12

Nerve terminal or synaptic bouton (knob)

Answer 12

End of the axon

Enlarged to maximize neurotransmission to the next neuron and ensure proper release of neurotransmitters

Question 13

Synaptic cleft

Answer 13

Small space between neurons into which the terminal portion of the axon releases neurotransmitters which bind to the postsynaptic neuron

Question 14

Synapse

Answer 14

The nerve terminal, synaptic cleft and postsynaptic membrane together

Question 15

Nerve

Answer 15

Multiple neurons bundled together in the PNS

Nerves may be sensory, mixed, or motor

Question 16

Tracts

Answer 16

In the CNS, axons bundled together
Only carry one type of info
Cell bodies of neurons in the same tract are grouped into nuclei

Question 17

Glial cells

Answer 17

Also called nueroglia
Often provide for support and myelination in CNS
Structural role

Question 18

Action potentials

Answer 18

Neurons use all or nothing messages to relay electrical impulses down the axon to the synaptic bouton
Ultimately cause the release of neurotransmitters
Initiated at the axon hillock

Question 19

Resting membrane potential

Answer 19

There is a an electrical potential (voltage) difference between the inside of a neuron and the extracellular space
Usually about -70mV with inside negative relative to outside

Question 20

Na+/K+ ATPase

Answer 20

Neurons are selectively permeable to this and ions to maintain the relatively negative internal environment
Ex for every two K+ ions moved into the cell, 3 Na+ are moved out at expense of one ATP

Also works to restore sodium and potassium gradient (sodium outside, potassium inside) after action potential

Question 21

Depolarization

Answer 21

Excitatory input causes this - it is the raising of the membrane potential (V m) from its resting potential
Makes neuron more likely to fire an action potential

Question 22

Hyper polarization

Answer 22

Inhibitory input causes this
It’s the lowering of membrane potential from its resting potential
Makes neuron less likely to fire action potential

Question 23

Threshold

Answer 23

If the axon hillock receives excitatory input to be depolarized to the threshold value (usually -55 to -40 mV) an action potential will be triggered

Question 24

Summation

Answer 24

The additive effect of multiple signals - some excitatory and some inhibitory

Question 25

Temporal summation

Answer 25

Multiple signals integrated during a relatively short period of time

Question 26

Spatial summation

Answer 26

Additive effects are based on number and location of incoming signals

Question 27

Electrochemical gradient

Answer 27

Promotes the migration of sodium into the cell | Interior is more negative and generally has more sodium ions than exterior

Question 28

Summary of sodium channel process membrane potential

Answer 28

Migration of sodium ion into cell Cell rapidly depolarizes (becomes positively charged) Vm approaches +35 mV sodium channels are inactivated and brought back near resting potential to be deinactivated Sodium channels- closed( before reaching threshold) open (from threshold to about +35 mV) inactive (from +35 back down) and back to closed (after inactivation has been reversed)

Question 29

Path of potassium during membrane potential

Answer 29

Sodium depolarizes cell causing efflux of potassium from neuron Positively charged K+ out of cell restores negative membrane potential called repolarization and then causes overshoot of resting potential called hyperpolarization

Question 30

Refractory periods

Answer 30

Caused by hyperpolarization due to massive efflux of K+ Absolute refractory period - no amount of stimulation can cause another action potential to occur Relative refractory period - must be greater than normal stimulation to cause action potential because membrane is more negative than resting

Question 31

Impulse propagation

Answer 31

For a signal to be conveyed to another neuron the action potential must travel down the neuron and initiate neurotransmitter release This movement is impulse propagation

Question 32

Saltatory conduction

Answer 32

The hopping of a signal from node of ranvier to node of ranvier on a myelinated axon Cross sectional increase promotes faster movement. Length means slower

Question 33

Presynaptic neuron

Answer 33

Neuron preceding synaptic cleft

Question 34

Postsynaptic neuron

Answer 34

Neuron after synaptic cleft | Also called an effector

Question 35

Neurotransmitter release

Answer 35

Prior to release held in vesicles Action potential reaches nerve terminal causes voltage gated calcium channels to open Sudden increase causes fusion of vesicles with cell membrane and causes exocytosis of neurotransmitter

Question 36

Regulation of neurotransmitters

Answer 36

By means of breakdown by enzymatic reactions (ex of acetylcholine (ACh) by acetylcholinesterase (AChE)) Can be brought back to synaptic cleft by reuptake carriers (Ex include serotonin: 5-HT, dopamine: DA, and norepinephrine (NE)) Or they can simply be diffused out of synaptic cleft such as Nitric Oxide NO

Question 37

Sensory neurons

Answer 37

Afferent neurons | Transmit info from receptors to the spinal cord and brain

Question 38

Motor neurons

Answer 38

Efferent neurons | Transmit info from the brain and spinal cord to muscles and glands

Question 39

Interneurons

Answer 39

Most abundant | Located in brain and spinal cord and often linked to reflexive behavior

Question 40

Functions of the nervous system

Answer 40

Sensation and perception Motor function, cognition and problem solving, executive function and planning, language comprehension and creation, memory, emotion and emotional expression, balance and coordination, regulation of endocrine organs, regulation of heart rate, breathing rate, vascular resistance, temperature, and exocrine glands

Question 41

Supraspinal circuits

Answer 41

Used when input is required from the brain unlike in most reflexive responses

Question 42

CNS

Answer 42

Brain and spinal cord

Question 43

PNS

Answer 43

Somatic and autonomic nervous systems Autonomic is made up of sympathetic and parasympathetic Connects the CNS and the rest of the body Consists of 31 spinal nerves and 10 of 12 pairs of cranial nerves

Question 44

Brain

Answer 44

Part of the CNS, composed of white matter - axons encased in myelin sheaths and lies deeper than grey matter - which is unmyelinated cell bodies and dendrites

Question 45

Spinal cord

Answer 45

Part of CNS - extends from brain stem and can be divided four ways: cervical, thoracic, lumbar and sacral Protected by vertebral column Composed of white and grey matter - grey is deep within. Axons of motor and sensory neurons are in the spinal cord

Question 46

Dorsal root ganglia

Answer 46

Cell bodies or sensory neurons which enter the back side of the spinal cord are found in this

Question 47

Somatic nervous system

Answer 47

Sensory and motor neurons distributed throughout the skin, joints and muscles Transmit info through afferent fibers

Question 48

Autonomic nervous system

Answer 48

ANS Regulates heartbeat, respiration, digestion, and glandular secretions Involuntary muscles associated with many internal organs and glands Helps regulate body temperature by activating sweating or piloerection Automatic

Question 49

Preganglionic neuron | And postganglionic neuron

Answer 49

two neurons in the autonomic nervous system that work in a series to transmit messages from the spinal cord Soma of preganglionic neuron is in the CNS and its axon travels to a ganglion in the PNS It synapses to the cell body or the postganglionic neuron and then affects the target tissue

Question 50

Subdivisions of the ANS

Answer 50

Parasympathetic and sympathetic

Question 51

Parasympathetic NS

Answer 51

Conserve energy Resting and sleeping states Reduce heart rate and constrict bronchi Digestion - increase peristalsis and exocrine secretions

Question 52

Acetylcholine

Answer 52

The neurotransmitter responsible for parasympathetic responses in the body and is released by both the pre and postganglionic neurons

Question 53

Vagus nerve

Answer 53

Cranial nerve X | Responsible for much of the parasympathetic innervation is the thoracic and abdominal cavity

Question 54

Sympathetic NS

Answer 54

``` Activated by stress Fight or flight reactions Increases HR, redistributes blood to muscles of locomotion, increases blood glucose concentration, relaxes the bronchi, decreases digestion and peristalsis, dilates the pupils to maximize light intake, releases epi into bloodstream Preganglionic releases acetylcholine Postganglionic releases norepi ```

Question 55

Reflex arcs

Answer 55

Control reflexive behavior Two types are monosynaptic reflex arc - single synapse bt sensory neuron that receives the stimuli and the motor neuron that responds to it (knee-jerk reflex) Polysynaptic reflex arc - at least one interneuron between sensory and motor neurons (withdrawal reflex - to maintain balance the other foot must be firmly planted on the ground which means the motor neuron in the opposite quadricep must be stimulated)