Lecture 2 - CNS, PNS and Neurons

Question 1

What is neuroanatomy?

Answer 1

Structure and connectivity of the nervous system

Question 2

What is neurophysiology?

Answer 2

how neurons work and communicate

Question 3

Describe the components of the nervous system.

Answer 3

Made up of CNS and PNS
CNS - brain and spinal cord
PNS - autonomic and somatic
Autonomic further divided into sympathetic and parasympathetic

Question 4

What is the function of the brain in the CNS?

Answer 4

Receives and processes information, initiates responses, stores memories, generates thoughts and emotions

Question 5

What is the function of the spinal cord in the CNS?

Answer 5

Conducts signals to and from the brain, controls reflex activities

Question 6

What is the role of the autonomic nervous system?

Answer 6

Controls Involuntary Responses
Consists of nerves responsible for:
- Regulates the automatic behaviors of the body (e.g., heart rate, blood pressure, respiration, digestion etc.)

Split into sympathetic - fight/flight
Parasympathetic - rest/digest

Question 7

What is the role of the somatic nervous system?

Answer 7

Controls Voluntary Movements
Consists of nerves responsible for:
Transmitting signals from the CNS to the body for voluntary movement (efferent)
Delivering sensory information from the body to the CNS (afferent)

Question 8

What is the hindbrain?

Answer 8

Consists of cerebellum medulla and pons

Question 9

What is the function of the medulla?

Answer 9

• Part of brain stem
• Responsible for regulating:
  Heart rate
  Circulation
  Respiration
  Sleep/wakefulness
  Level of arousal/consciousness
  Reflexes (e.g., swallowing, coughing & sneezing, vomiting)
• Origin point of cranial nerves IX-XII (responsible for sending and receiving motor and sensory information to and from pharynx, larynx, oesophagus, posterior third of the tongue, heart and digestive system)

Question 10

What is the pons? And its function?

Answer 10

In hindbrain
Part of brain stem

‘Pons’ – means bridge in Latin
Contains various tracts linking the cerebral cortex to the cerebellum and the spinal cord
Responsible for regulating:
Arousal (brain attentiveness)
Sleep
Dreaming
Origin point of cranial nerves V-VIII (responsible for sending and receiving motor and sensory information to and from the head, face, eyes, inner ear, and anterior two thirds of the tongue)

Question 10

What is the cerebellum? And its function?

Answer 10

In hindbrain
Not part of brain stem
Contains over 50% neurons in brain
Responsible for:
Fine motor coordination
Motor learning
Balance
Gait and posture
Proprioception
More recently considered to contribute to cognitive and affective processes

Question 10

What is the midbrain? And its function?

Answer 10

Superior most part of the BRAINSTEM (medulla, pons, midbrain)
Origin point of cranial nerves III-IV (responsible for innervating eye muscles)
Separated into tectum posteriorly and tegmentum anteriorly

Question 10

What is the tectum?

Answer 10

Superior Colliculus – orients towards visual stimuli
Inferior Colliculus – orients towards auditory stimuli

Question 11

What is the tegmentum?

Answer 11

contains neurotransmitter nuclei involved in movement and arousal

Question 12

What are the subcortical structures of the forebrain?

Answer 12

Limbic system, basal ganglia, hypothalamus, thalamus

Question 13

What is the cerebral cortex?

Answer 13

Outermost layer of forebrain
Characterised by gyri and sulci. Responsible for our higher order cognitive functions as well as sending and receiving sensory and motor input and output.

Question 14

Function of the frontal lobe

Answer 14

Movement, Executive Function, Working Memory, Judgement

Question 15

Function of the parietal lobe

Answer 15

Somatosensory processing, attention, higher order visual processing

Question 16

Function of the occipital lobe

Answer 16

visual processing

Question 17

Function of the temporal lobe

Answer 17

Hearing, memory, higher or visual processing

Question 18

What is the thalamus?

Answer 18

The relay station of the brain. Receives and filters input from the senses (excluding olfaction) and transmits to the cerebral cortex

Question 19

What is the hypothalamus?

Answer 19

Regulates the endocrine system and the ANS. Controls body temperature, hunger, thirst and sexual behaviour.

Question 20

What is the limbic system?

Answer 20

Made up of several structures including the thalamus and hypothalamus. Vital for motivation, emotion, learning and memory.

Question 21

What is the basal ganglia?

Answer 21

Made up of several structures including the putamen and caudate. Vital for initiation and direction of voluntary movement.

Question 22

What are the 12 cranial nerves?

Answer 22

1. Olfactory 2. Optic 3. Oculomotor 4. Trochlear 5. Trigeminal 6. Abducens 7. Facial 8. Vestibulocochlear 9. Glossopharyngeal 10. Vagus 11. Spinal Accessory 12. Hypoglossal

Question 23

What are the key components of a neuron?

Answer 23

cell body dendrites axon

Question 24

What are receptors?

Answer 24

specialized neural components responsive to specific types of energy (external stimuli)

Question 25

Describe the structures of a neuron

Answer 25

Cell body (soma) - contains the nucleus of a neuron Dendrite – tree branch-like structures extending from cell body, receiving electrical signal from terminal buttons of other neurons Axon - Long thin structure that carries electrical impulse away from cell body towards terminal buttons Terminal button – bud at the end of a branch of an axon – forms synapses with other neurons Synapse – Junction between terminal button and membrane of another neuron Neurotransmitter – chemical released by terminal buttons (can have excitatory or inhibitory effect on other neurons) Glial cell - supporting cell that occurs in both the central and peripheral nervous system (e.g., oligodendrocytes, astrocytes and microglia) Myelin Sheath – extension of a glial cell that wraps around the neuronal axon to provide insulation and facilitate electrical transmission Nodes of Ranvier – a naked portion of a myelinated axon between adjacent glial cells helping to speed up electrical conduction

Question 26

What are the consequences of myelin damage?

Answer 26

Damage to myelin coating affects neuronal function Multiple sclerosis - an autoimmune disease affecting myelin and myelin producing glial cells in the CNS Fatigue Impaired motor function Impaired sensory function (vision problems, tingling, pain) Cognitive impairment

Question 27

What is resting potential?

Answer 27

the difference in electric charge between the inside and outside of a neurons cell membrane (-70mv)

Question 28

What is action potential?

Answer 28

electrical signal that is conducted along the length of the neuron’s axon to a synapse

Question 29

What are the stages of action potential?

Answer 29

Depolarisation Repolarisation Hyperpolarisation (Refractory period) Return to resting potential

Question 30

Describe depolarisation

Answer 30

Electrical signal from receptor causes some Na+ channels to open and cell to depolarise Once threshold potential (-55mv) is met, all Na+ channels open resulting in further depolarization

Question 31

Describe repolaristation and hyperpolarisation

Answer 31

At peak depolarization (once Na+ reach equilibrium across the membrane) Na+ channels begin to close K+ channels now open K+ diffuses out of the cell causing the membrane potential become more negative (repolarise) K+ continues to flow out of the cell causing the membrane potential to drop below that of the resting state (hyperpolarization)

Question 32

Describe the return to resting state

Answer 32

Active process Pumps three Na+ ions out and two K+ ions in Returns membrane to resting potential

Question 33

What are the properties of action potentials?

Answer 33

A propagated response along the axon Remain the same size regardless of stimulus intensity Upper firing rate is 500-800 impulses per second Firing rate increases with increased stimulus intensity Show spontaneous activity without stimulation

Question 34

What happens during neurotransmission?

Answer 34

Neurotransmitters: Relatively small molecules or peptides Released by presynaptic neuron Received by post-synaptic neuron Matched with specific receptors Facilitate change in membrane potential of post-synaptic neuron

Question 35

What is an excitatory response?

Answer 35

response of a nerve fibre in which the firing response increases e.g. glutamate

Question 36

What is and inhibitory response?

Answer 36

response of a nerve fibre in which firing rate decreases e.g. GABA

Question 37

What is summation of the inhibitory and excitatory inputs?

Answer 37

If excitatory input stronger than inhibitory then neuron’s firing rate is high If inhibition greater than excitation neuron’s firing rate is reduced Firing rate is determined by shared inputs from excitatory and inhibitory neurotransmission

Question 38

How does neurotransmission stop?

Answer 38

Reuptake – the neurotransmitter is transported back to the presynaptic cell to be recycled Autoreception – autoreceptors in presynaptic cell inhibit further neurotransmitter release or synthesis Enzyme degradation – a neurotransmitter is broken down by enzymes in the synaptic cleft