nervous system-cells of the CNS and PNS

Question 1

what are the 2 broad categories of cells that make up the nervous system?

Answer 1

 Neurons (Never cells)

 Supporting cells (Glial cells)

Question 2

what is a Neuron?

Answer 2

◦ basic structural and functional unit of the nervous system

◦ capable of generating and conducting an action potential

◦ communicate with other cells by means of a chemical or electrical synapse

Question 3

what is a Supporting cells (Glial cells)?

Answer 3

◦ support, insulate and maintain neurons
◦ Neuroglia (nerve glue) in CNS
◦ 2 types in PNS: Schwann cells & Satellite cells

Question 4

what is the structure of a Neuron?

Answer 4

 Cell body

 Axon

 Dendrites

Question 5

what is the Cell body?

Answer 5

◦ Houses the control centre

◦ Contains a single relatively large nucleus

Question 6

what is the Axon?

Answer 6

◦ A single axon conducts action potentials away from the neuron cell body

◦ End of axon terminals which communicate with other cells
by means of a chemical or electrical synapse

◦ A nerve is a bundle of axons

Question 7

what is the Dendrites?

Answer 7

◦ Conduct action potentials towards the neuron Cell body

Question 8

what are the functional classifications of Neurons

Answer 8

• Sensory or afferent: action potentials toward CNS.
• Motor or efferent: action potentials away from CNS.
• Interneurons or association neurons: within CNS from one neuron to another.

Question 9

what are the structural classification of Neurons?

Answer 9

• Multipolar
• Bipolar
• Pseudo-unipolar
• Anaxonic

Question 10

what are Multipolar neurons?

Answer 10

most neurons in CNS; motor neurons.

Question 11

what are Bipolar neurons?

Answer 11

sensory in retina of the eye and nose.

Question 12

what are Pseudo-unipolar neurons?

Answer 12

single process that divides into two branches. Part that extends to the periphery that has dendrite-like sensory receptors.

Question 13

what are Anaxonic neurons?

Answer 13

no axons, only dendrites; found in brain and retina where they only communicate using
graded potentials.

Question 14

where are the sensory receptors located?

Answer 14

Located in the skin, muscles, joints and internal organs

Question 15

what are the 5 receptors we need to know about?

Answer 15

 Chemoreceptors
◦ Generate action potential in response to specific chemical stimuli

 Photoreceptors
◦ Generate action potentials in response to visible light

 Thermoreceptors
◦ Generate action potentials in response to temperature

 Mechanoreceptors
◦ Generate action potentials in response to physical force

 Nociceptors
◦ Generate action potentials in response to tissue/ cell damage

Question 16

what are the 5 parts of a reflex arc?

Answer 16

1. Sensory Receptor
2. Afferent/Sensory neuron
3. Association/Inter neuron
4. Efferent/Motor neuron
5. Effector organ

Question 17

what is the stretch reflex?

Answer 17

• Simplest reflex
• Maintains posture
• i.e. knee-jerk reflex

Question 18

what is the Golgi tendon reflex?

Answer 18

• Prevents excessive pressure to tendons
• Reflex not always adequate for athletes
• i.e. Weight lifters suddenly dropping heavy weight

Question 19

what is the withdrawal reflex?

Answer 19

• Remove limb from pain.

Question 20

what is the first stage of the stretch reflex?

Answer 20

muscle spindles detect stretch of the muscle

Question 21

what is the second stage of the stretch reflex?

Answer 21

sensory neuron conduct action potentials to the spinal cord. Collaterals extend to the brain

Question 22

what is the third stage of the stretch reflex?

Answer 22

Sensory neurons synapse directly with alpha motor neurons, which also receive signals from the brain via the upper motor neuron

Question 23

what is the fourth stage of the stretch reflex?

Answer 23

Alpha motor neurons conduct action potentials to the muscle, causing it to contract and resist being stretched.

Question 24

what is the fifth stage of the stretch reflex?

Answer 24

Gamma motor neurons conduct action potentials from the spinal cord to the muscle fiber of the muscle spindle to cause the spindle to contract. this maintains proper tension within the spindle as the muscle contracts.

Question 25

what is the first stage of the Golgi tendon reflex?

Answer 25

Golgi tendon organs detect tension applied to a tendon.

Question 26

what is the second stage of the Golgi tendon reflex?

Answer 26

Sensory neurons conduct action potentials to the spinal cord.

Question 27

what is the third stage of the Golgi tendon reflex?

Answer 27

Sensory neurons synapse with inhibitory interneurons that synapse with alpha motor neurons

Question 28

what is the fourth stage of the Golgi tendon reflex?

Answer 28

Inhabitation of the alpha motor neurons cause muscle relaxation, relieving the tension applied to the tendon.

Question 29

what is the first stage of the withdrawal reflex?

Answer 29

Pain receptors detect a painful stimulus.

Question 30

what is the second stage of the withdrawal reflex?

Answer 30

Sensory neurons conduct action potentials to the spinal cord.

Question 31

what is the third stage of the withdrawal reflex?

Answer 31

Sensory neurons synapse with excitatory interneurons that synapse with alpha motor neurons.

Question 32

what is the fourth stage of the withdrawal reflex?

Answer 32

Excitation of the alpha motor neurons results in contraction of the flexor muscles and withdrawal of the limb from the painful stimulus.

Question 33

what does the Spinal nerve consist of?

Answer 33

• Axon bundles.
• Schwann cells.
• Connective tissue.

Question 34

what does the connective tissue in the spinal nerve consist of?

Answer 34

• Endoneurium: surrounds individual neurons.

• Perineurium: surrounds axon groups to form
fascicles.

• Epineurium: surrounds
the entire nerve.