Week 2 - Neuroanatomy

Question 1

What is the fundamental difference between somatic nervous system and autonomic nervous system? Explain in terms of afferent and efferent.

Answer 1

Somatic Nervous System (SNS)
(interaction with environment)
Afferent nerves (sensory - to CNS)
Efferent nerves (motor - from CNS)

Autonomic Nervous System(ANS)
(Regulates the body’s internal state)
Afferent - from internal organs
Efferent - to internal organs
Sympathetic and parasympathetic nerves (both efferent)

Question 2

What are the two types of efferent nerves in autonomic nervous system?

Answer 2

1. Sympathetic
   Stimulate (“winds things up”, organise energy in threatening situations)
2. Parasympathetic (“winds things down”)
   conserves energy

Organs receive inputs from both (push / pull relationship).

Question 3

What are the clusters of cells in the CNS/PNS?

Answer 3

Nuclei for CNS and Ganglia for PNS

Question 4

What are the clusters of axons in the CNS/PNS?

Answer 4

Tracts for CNS and Nerves for PNS

Question 5

What are “poles”?

Answer 5

number of directions for transmission by a neuron

Question 6

What are the two main types of glial cells in the CNS and PNS? and what is the ratio of glial cells to neurons?

Answer 6

Oligodendrocyte for CNS
Schwann cells in PNS

Glial cells outnumber neurones 10:1.

Question 7

What are the four main types of neurons?

Answer 7

1. Unipolar neuron - sensory neurons transfer information from receptor cells to higher nerve cells
2. Bipolar Neuron - connecting adjacent cells; typically in sensory system
3. Multipolar neuron (typical neuron diagram) - transfer information between cells within a single structure; can collect info from many cells
4. Multipolar neuron - connecting adjacent cells and only has a cell body.

Question 8

What are the two main types of neurons in the spinal cord (explain in terms of dorsal, ventral, afferent and efferent).

Answer 8

Unipolar afferent neurons join the dorsal horn - both somatic (skeletal / sensory) and autonomic (internal organs) systems.

Multipolar efferent neurons have their cell bodies in the ventral root. Their axons project out to somatic and autonomic systems.

Question 9

What are the three neurophysiological features important for protecting the brain?

Answer 9

Skull
Meninges (Dura Mater, Pia Mater, Arachnoid)
Cerebrospinal fluid (CSF)

Question 10

What is the chemical protection mechanism of the brain?

Answer 10

Chemical protection – maintaining chemical balance
The blood-brain barrier
Tightly packed cells along the blood vessel walls of the CNS prevent entry of many (large) molecules.
Good and bad (eg L-Dopa)

Question 11

From the scalp to the outer layer of the cortex, what is the seven ascending order of protection. From outermost to innermost layer.

Answer 11

1. Scalp
2. Skull
3. Dura Mater
4. Arachnoid meninx or membrane
5. subarachnoid space (CSF flow
6. Pia Mater meninx
7. Cortex

Question 12

Where is the CSF produced and what happens if drainage of CSF is blocked?

Answer 12

Choroid plexus in the fourth ventricle.

If drainage is blocked: hydrocephalus

Question 13

What is the Myelencephalon? And what is it’s role?

Answer 13

Medulla oblongata

Primarily composed of axonal tracts carrying information from the brain to the body and back.

Vital functions- heart rate, breathing

Contains portion of reticular formation (net-like formation) - role in arousal.

Question 14

What is the Metencephalon?

Answer 14

Pons and Cerebellum

Also composed of many tracts of nerves and contains a portion of the reticular formation.

Pons – vital functions relay centre, plays a role in mediating REM sleep.

Cerebellum - sensory and motor control; cognitive; navigation

Question 15

What is the Mesencephalon and the two main regions?

Answer 15

The midbrain:

Tectum
superior colliculus -visual orienting of attention
inferior colliculus -auditory orienting of attention

Tegmentum – portion below tectum
periaqueductal grey matter - autonomic function, motivation, response to threat, descending pain modulation
Substantia Nigra - motor control

Question 16

What is the famous case of the Frozen Addicts?

Answer 16

the discovery of the cause of a local outbreak of sudden, severe parkinsonism in a group of young adults in northern California and how this discovery led to greater insight into Parkinson’s disease.

led a team of investigators to pinpoint the toxicant responsible for the acute loss of dopamine-containing neurons in the substantia nigra, causing the parkinsonism in these patients.

The toxicant was MPTP (pyridine) an unwanted biproduct from a short step synthesis of an illicit synthetic heroin analogue.

Question 17

What are the three main nucleus of the Thalamus?

Answer 17

Thalamus (Diencephalon):
1. Lateral Geniculate Nucleus - first synapse after the optic nerve leaves the eye.
2. Medial Geniculate Nucleus - Auditory relay
3. Ventro Posterior Nucleus - Sensorimotor relay.

Question 18

What are the two main cell types of the neo-cortex layers?

Answer 18

1. Pyramidal Cells (large bodies, multipolar, long axon goes down and inward through layers)
2. Stellate Cells (small, star-shaped short / no axons; transmit info laterally)

Question 19

How does each neo-cortical layers differ in the quantitative aspects of pyramidal and stellate cells.

Answer 19

Each layer differs
in the relative concentration of stellate and pyramidal cells
in the relative size and concentration of cell bodies (e.g. layer IV is thick in sensory areas; layer V – mainly pyramidal cells with long axons - in motor areas)

Question 20

How does information pass down the neocortical layers?

Answer 20

Vertical flow of information via long axons is the basis of columnar organisation.

Question 21

What is commisurotomies/callosotomies?

Answer 21

Antecedent: usually epilepsy
Procedure: callosotomy, anterior commisurotomy
Consequence: reduction of seizures
Behavioural consequence: very little
Experimental consequence: sensory information presented to one hemisphere is not available to guide behaviour in the other hemisphere