chapter 12

Question 1

sensory functions

Answer 1

sensory input from receptors detect changes (body temp, blood pressure, etc) inside and outside the body

Question 2

interactive function

Answer 2

sensory input is interpreted and coordinated with an appropriate motor response

Question 3

motor function

Answer 3

motor output to an effecter organ sich as a muscle or gland

Question 4

efferent

Answer 4

same as a motor pathway, but brings information out

Question 5

central nervous system

Answer 5

brain and spinal cord

Question 6

peripheral nervous system

Answer 6

cranial and spinal nerves, ganglia and sensory receptors
can be further divided into
sensory division
motor division

Question 7

PNS sub division- sensory division

Answer 7

brings information from sensory receptors throughout the body to the CNS
it carries somatic sensory info (touch, temp, pain, proprioception etc.)
also carries special senses info (smell, taste, vision, hearing, equilibrium)

Question 8

PNS sub divisions MOTOR DIVISION

Answer 8

motor neurons conduct impulses from CNS to effectors (muscles and glands).
This division is further sub-divided into:
a) somatic nervous system
b) autonomic nervous system

Question 9

somatic nervous system

Answer 9

under voluntary control
Motor neurons conduct impulses from CNS to skeletal muscles

Question 10

autonomic nervous system

Answer 10

under involuntary control
Motor neurons conduct impulses from CNS to smooth and cardiac muscle and to glands.

Question 11

two divisions of the autonomic nervous system

Answer 11

Sympathies -> “fight-or-fight”
Parasympathetic -> “rest-and-digest”

Question 12

neurons

Answer 12

functional units of the nervous system
Most are unable to undergo mitosis. Can’t undergo cell division, because they might be missing some organelles like centrioles, one theory for this is because you want to limit the number of neurons so you don’t over load the system. It already is a very complex system in the body.
Require abundant supply of O2 and glucose

Question 13

properties of neurons

Answer 13

Irritability- highly responsive to stimuli. They can react to any sort of change coming from the environment.
Conductivity- transport info from one part to another
generate and propagate action potentials (nerve impulses)

Question 14

neuroglia

Answer 14

(“glue that hold nerves tissue together”)
are supportive and protective cells that aid neurons
Smaller and more numerous than neurons (10:1) and are still capable of mitosis
There are 6 types:
Astrocytes, oligodendrocytes, microglia and ependymal cells are found in the CNS
Schwann cells and satellite cells found in the PNS

Question 15

neurons in the CNS

Answer 15

Cell body (soma) -> nucleus, organelles, nissl bodies (big clusters of rough ER and ribosomes that are creating proteins), neurofibrils ( kind of microtubule that helps with structural support and cell shape)
Cell body lacks centrioles
dendrite(s) -> “receiving” process(es) that carry information TOWARDS the cell body. (Short, tampered and highly branched) many in each cell

Question 16

axons

Answer 16

a process that carries information AWAY from the cell body. It eventually divides into many axon terminals. One in each cell

Question 17

axons in the CNS

Answer 17

These can be:
myelinated -> covered by layers of neuroglia cells membrane (lipid/protein material).
Myelin sheath act as an insulator.
PNS -> Schwann cell wraps around axon
CNS -> oligodendrocyte has many processes that wrap around many axons
Space b/t cells are Nodes of Ranvier

b) unmyelinated -> are surrounded by a thin Schwann cell membrane that encloses several axons
Smaller in diameter,

Axons are never “naked” they always have some covering around them.

Question 18

grey matter

Answer 18

consists of neuron cell bodies
neurone, cell bodies, dendrites, unmyelinated axons, axon terminals, neuroglia

Question 19

white matter

Answer 19

consists of neuron processes mainly myelinated axons (myelin sheath = white colour)
myelinated axons of neurons

Question 20

nucleus

Answer 20

cluster of neuron cell bodies in the CNS

Question 21

ganglion

Answer 21

cluster of neuron cell bodies in the PNS

Question 22

tract

Answer 22

bundle of neuron processes in the CNS

Question 23

nerve

Answer 23

bundle of neuron processes in the PNS

Question 24

neurophysiology

Answer 24

Neruons are electrically excitable cells, they are called this because they have ion\protein channel. They also have resting membrane potential. Membrane potential is a potential difference (voltage)- difference of charge built up on either ends.

Question 25

ion channels

Answer 25

Ions diffuse down an electrochemical gradient through a channel protein
they travel from areas of high concentration to areas of low concentration
They also travel from areas that are charged to are that are oppositely charged (i.e +ve to -ve and from -ve to +ve)
Channel proteins are ion-selective

Question 26

Leake channels

Answer 26

gates randomly open and close
There are more K+ leak channels then Na+ leak channels in the cell membrane
Membrane is more permeable to K+ then Na+

Question 27

ligand-gated channels

Answer 27

open and close in response to a certain
Chemical 9e.g., neurotransmitter, hormones, ions).

Question 28

mechanically -gated channels

Answer 28

open or close in response to a mechanical stimulus (e.g., vibration, touch, pressure, stretch). (Think about a garbage bin)

Question 29

voltage gated channels

Answer 29

open in response to a change in membrane potential (voltage)

Question 30

resting membrane potential

Answer 30

Difference in electrical charge exists across the cell membrane; the resting membrane potential (-70mV)
Is maintained by an unequal ion distribution across the membrane

Question 31

outside the cell

Answer 31

extracellular fluid

Question 32

inside of cell

Answer 32

intracellular fluid

Question 33

generation of an action potential

Answer 33

An AP involves a series of rapidly occurring events that decrease and reverse the membrane potential and then restores it to the resting stage
An AP occurs in response to a threshold stimulus
A neuron exhibits an “all-or-none” response

-55mV has to be reached to start a nerve impulse.

Question 34

depolarizing phase

Answer 34

A stimulus causes the membrane to depolarize to threshold
voltage-gates Na+ channels are quick to open upon depolarization
Influx of Na+ causes membrane to depolarize even more (become less negative inside)
More Na+ channels open and membrane potential becomes +30mV
Na+ channels start to close

Question 35

re-polarizing phase

Answer 35

K+ channels are slower to open upon depolarization (Na+ channels are now closing)
K+ diffides out of the neuron
Membrane repolarizes (becomes more negative

Question 36

after- hyper polarizing phase!!!

Answer 36

Excess K+ leaves (K+ channels slow to close) and membrane hyperpolarizes (reaches -90mV)
as K+ channels close, membrane potential returns to -70mV.

Duration of a neuron AP is about 1 msec
Ion distributions of the resting state are restored by the Na/K pump
Neuron has a refractory period (RP); time period when a second AP can’t be generated
During this the neuron is unresponsive, the advantage of this is it insures that each AP is separate, because each AP gives a different signal, but it also makes sure that there is one way of flow of information.

absolute RP: an AP is not possiblefrom the time of opening of sodium channels, to the end of depolarization (where sodium and potassium channels are closed).
Relative RP: require a stronger stimulus to generate an AP. Can have a second action potential generated but for that to occur the stimulus needs to be stronger.
Absolute refractory period- AP is propagated towards the axon terminals

keeps its strength as it spreads along the membrane
As Na+ flows inward, voltage-gated Na+ channels open in adjacent area of the membrane
AP regenerates over and over at adjacent ares of the membrane

Question 37

continuous condition

Answer 37

slow process
occurs along unmyelinated axons
Slow process because there is no insulation. No area where there is insulation.
energy expensive process. after every AP there are sodium potassium pumps along the whole “route” which use up lots of energy

Question 38

saltatory conduction

Answer 38

much faster conduction)
occurs along myelinated axons
Depolarization only at nodes
AP jumps from node to node
Number of impulses per sec increases with intensity of stimulus
30 times faster on average. Insulated axons by the myelin sheath. Where there is insulation there are no ions floating around. Only places you will see ions floating around are at the nodes of ranvier. More energy efficient, because you only need potassium pumps at the nodes of ranvier.

Question 39

transmission across synapses

Answer 39

A synapse is a junction between:
2 neurons -> can be axodendritic, axiomatic or axoaxonic
A neutron and its effector (e.g, neuromuscular junction).
Axodensrritic- junction between axon of one neuron and a dendrite on another neuron.
axiomatic- junction between the cell body
axoaxonic- axon to axon.

Question 40

what happens at neurone synapse

Answer 40

1st neuron is the presynaptic (before the junction) and 2nd neuron is the postsynaptic (after the junction). They’re separated by a space called the synaptic cleft. - very small space that separates the two neurones, they are close together but are never touching which is the junction.

A synapse is unidirectional (goes in one direction.)
An electrical impulse can’t cross cleft. Therefore, it’s converted to a chemical signal, which involves the release of a neurotransmitter.
The neurotransmitter binds to receptors on the membrane off the postsynaptic cell and generates an electrical signal, a postsynaptic potential.

About 50 substance in our body that are used as neurotransmitters.