Nervous System

Question 1

3 Keys to the Nervous system

Answer 1

1. The nervous system senses the environment, processes information, and responds. 2. Neural signals are fast, fleeting, and specific; endocrine signals are slow, sustained, and general. 3. The type and number of channels and receptors are the hidden determinants of many cellular and systemic phenomena.

Question 2

How is chemical communication accomplished in the nervous system?

Answer 2

1. Neurotransmitters

Question 3

How is chemical communication accomplished in other systems?

Answer 3

1. Paracrine: local mediators 2. Endocrine system: hormones

Question 4

Differences between nervous system, paracrine system, and endocrine system

Answer 4

Nervous system: rapid and direct communication between specific parts of the body, allowing quick but short-lived changes. Neurotransmitters travel over very short distances. Endocrine system: generalized, slow, and sustained compared to nervous system. Hormones travel throughout the body. Paracrine system: lies somewhere between the extremes of nervous system and endocrine systems. Local mediators travel intermediate distance.

Question 5

Nervous system function

Answer 5

Integrates information it obtains from the environment and decides how to respond. Some of this is automatic while some can be controlled.

Question 6

Nervous system mechanism

Answer 6

Physical signal from environment –> chemical signal in body –> electrical signal

Question 7

Central Nervous System

Answer 7

made of the brain and spinal cord. Major function is to integrate nervous signals between sensory and motor neurons.

Question 8

Peripheral Nervous system

Answer 8

The CNS transmits information to the rest of the body through the PNS. The PNS handles the sensory and motor functions of the nervous system. Two parts of PNS:

1. Autonomic Nervous System - controls automatic/involuntary responses. Divided into sympathetic and parasympathetic nervous system.
2. Somatic Nervous System - controls voluntary responses

Question 9

Neuron

Answer 9

A specialized cell capable of transmitting a signal from one cell to another through a combination of electrical and chemical processes Neurons are post-mitotic: they cannot divide Neurons rely on glucose but does not use insulin for glucose transport the way other cells do

Question 10

Physical makeup of the neuron

Answer 10

1. dendrites 2. cell body 3. axon

Question 11

Intensity of a stimulus

Answer 11

Depends on the frequency of firing

Question 12

Summation

Answer 12

occurs in the cell body

Question 13

Axon hillock

Answer 13

Receives the sum of signals from the cell body and fires an action potential if there is enough

Question 14

Neuronal signal mechanism

Answer 14

Dendrites receive signals; cell body sums the signals; axon hillock fires action potential; electrical signal carried by axon; neurotransmitter carries chemical signal across synapse

Question 15

Concentration of ions

Answer 15

1. K+ high inside the cell [120 mM inside; 4 mM outside] 2. Na+ high outside the cell [14 mM inside; 140 mM outside] 3. Cl- high outside [4 mM inside; 105 mM outside]

Question 16

Resting membrane potential

Answer 16

-70 mV Determined by the equilibrium potential of potassium

Question 17

How do we maintain a resting membrane potential of -70 mV?

Answer 17

1. Na+/K+ ATPase pump - maintains potassium high inside the cell and sodium high outside the cell. Pumps 3 sodium out for every 2 sodiums that come in. 2. Permeability of K+ is greater than the permeability of Na+ at rest - This means K+ can flow out of the cell more than Na+ can come in, which leaves the inside of the membrane negatively charged. NOTE: the inside of the cell is not negatively charged, just the inner membrane of the cell.

Question 18

Chemical diffusion gradient and electrical gradient

Answer 18

The chemical gradient is caused by the difference in concentration between K+ inside the cell and K+ outside the cell (recall K+ is the major determinant at rest because the membrane is more permeable to K+ than to Na+). As the chemical gradient decreases (b/c K+ flows across membrane), an electrical gradient increases. The electrical gradient is the result of positively charged K+ ions outside the cell and negatively charged substances alone the inner side of the membrane.

Question 19

Action Potential

Answer 19

See graph

1. Stimulus is received –> local current flow causes upward drift
2. Sodium-gated ion channel opens –> resting membrane potential goes positive b/c sodium flows into the cell bringing its positive charge.
3. At peak of graph, sodium channels inactivate AND potassium channels open –> positive charge stops flowing in and positive charge starts flowing out
4. Hyperpolarization due to how quickly K+ rushes out

Question 20

Absolute Refractory period

Answer 20

when no stimulus can cause another action potential

Question 21

relative refractory period

Answer 21

when an abnormally large stimulus will create an action potential

Question 22

6 types of glial cells

Answer 22

1. microglia
2. ependymal cells
3. satellite cells
4. ascrocytes
5. oligodendrocytes
6. Schwann cells

Question 23

Microglia

Answer 23

Central nervous system’s macrophages - arise from white blood cells called monocytes. Carry out immune function

Question 24

ependymal cells

Answer 24

epithelial cells that line the space containing the cerebrospinal fluid. Use cilia to circulate the CSF.

Question 25

Satellite cells

Answer 25

support ganglia, which are groups of cell bodies in the peripheral nervous system

Question 26

Astrocytes

Answer 26

star-shaped neuroglia in the central nervous system that give physical support to neurons and help maintain the mineral and nutrient balance in the interstitial space

Question 27

Oligodendrocytes

Answer 27

wrap many times around axons in the central nervous system, creating myelin

Question 28

Schwann cells

Answer 28

produce myelin in the peripheral nervous system

Question 29

White matter

Answer 29

myelinated axons appear white and are called white matter

Question 30

Grey matter

Answer 30

Neuronal cell bodies appear grey and are known as grey matter

Question 31

myelin

Answer 31

increases the rate at which signals can travel down an axon

Myelin is a non-conductive insulator, which means it reduces the capacitance of the axon (which is the amount of charge it can store), so it encourages ion FLOW instead of STORAGE.

Question 32

nodes of Ranvier

Answer 32

tiny gaps between myelinated areas. Action potentials jump from node to node in order to avoid the resistance of the myelinated parts of the axon.

Question 33

saltatory conduction

Answer 33

The process of an action potential jumping from one node of Ranvier to another

Question 34

Sensory/afferent neurons

Answer 34

receive signals from a receptor cell that interacts with the environment and then transfer this signal to other neurons. Located dorsally (toward the back) on the spinal cord

Question 35

Interneurons

Answer 35

transfer signals from neuron to neuron. 90% of neurons in the human body are interneurons

Question 36

Motor neurons (effector/efferent neurons)

Answer 36

carry signals to a muscle or gland called the effector. Located ventrally (toward the front or abdomen) on the spinal cord.

Motor neurons are EFFerent b/c they cause the body to make an EFFort to respond to sensory information.

Question 37

reflex

Answer 37

a quick response to a stimulus that occurs without direction from the CNS, but does not occur independently of the CNS. That is, information about the stimulus is sent to the CNS as reflex is generated and the CNS can them modulate the response.

Question 38

stretch reflex

Answer 38

Muscle stretches –> sensory neuron signals a motor neuron in spinal cord –> motor neuron neuron makes muscle contract again and regain its resting length

Question 39

dorsal root ganglion

Answer 39

contains the snensory neuron cell bodies of the peripheral nervous system

Question 40

somatic motor neurons

Answer 40

innervate only skeletal muscle, which is involved in voluntary movement. The cell bodies of somatic motor neurons are located in the ventral horns of the spinal cord.

These neurons synapse directly on their effectors and release the neurotransmitter acetylcholine.

Question 41

Sympathetic Nervous system

Answer 41

A subset of the peripheral nervous system

“Fight or Flight”

Cell bodies of neurons are far from effectors

Main neurotransmitter: epinephrine/norepinephrine

Receptors: adrinergic

Question 42

Parasympathetic Nervous system

Answer 42

A part of the autonomic nervous system

“Rest and digest”

Cell bodies of neurons are close to effectors

Main neurotransmitter; Ach

Receptors: cholinergic (muscarinic and nicotinic)

Question 43

Ganglia

Answer 43

gangs of cell bodies in the PNS

Question 44

Nuclei

Answer 44

groups of cell bodies in CNS