Neuroanatmoy

Question 1

Define the following:

1. Peripheral Nervous System
2. Central Nervous System
3. Foramen magnum
4. Neuron

Answer 1

1. all parts outside of the bone casings of the skull and spinal cord
2. all parts inside the skull and spinal column (brain and spinal cord)
3. hole at the base of the skull, where the brain connects to the spinal cord
4. specialised nervous system cells. Collection of neurons is a nerve

Question 2

What are afferent and efferent nerves?

Answer 2

Afferent = ascending
Efferent = descending

Question 3

How does info enter and exit the spinal cord?

Answer 3

Information enters and exits the spinal cord via spinal nerves

Question 4

Define;

1. Dermatomes
2. Myotomes

Answer 4

1. Area of SKIN innervated by nerves related to a particular segment of the spinal cord
2. MUSCLES that are innervated by nerves related to a particular segment of the spinal cord

Question 5

What is gray matter and where do you find it and white matter?

Answer 5

• a collection of neuron cell bodies appear gray
• areas of the CNS with a large collection of cell bodies are called GRAY MATTER
• the CNS is a central cavity surrounded by gray matter, external to which is WHITE MATTER

Question 6

Briefly describe what the dorsal root is

Answer 6

The dorsal root of the spinal nerve (or posterior root of the spinal nerve) is one of two “roots” which emerge from the spinal cord.
Afferent nerves from the spinal cord are bundled at the back in the dorsal root

Question 7

Briefly describe what the ventral root is

Answer 7

The ventral root (or anterior root) is the efferent motor root of a spinal nerve.
Efferent nerves leaving the spinal cord are bundled together at the front in the ventral root

Question 8

What are peripheral nerves, and give some examples

Answer 8

Once out of the spinal column, the spinal nerves run down the limbs, becoming peripheral nerves.

• ulna nerve
• cranial nerve
• radial nerve
• median nerve
• sciatic nerve
• femoral nerve

Question 9

Name and describe the 3 main components of the brain

Answer 9

3 main structural divisions:
- the cerebrum
- the brainstem
- the cerebellum
At the base of the brain is the brainstem, which extends from the upper cervical spinal cord to the diencephalon of the cerebrum.
The brainstem is divided into the medulla, pons, and midbrain.
Posterior to the brainstem lies the cerebellum.

Question 10

Briefly describe the brainstem, including;

1. what it links
2. what it is comprised of
3. name of nerves it sources
4. the role

Answer 10

1. The brainstem sits at the base of the brain and connects the cerebrum and the spinal cord
2. Compromises the midbrain (superiorly), pons and the medulla oblongata (inferiorly)
3. It provides the main motor and sensory nerve supply to the face and neck via the cranial nerves.
4. Controls autonomic functions such as breathing, heart rate, and blood pressure

Question 11

Describe the cranial nerves and give some examples

Answer 11

12 pairs of nerves that emerge directly from the brain (including the brainstem).
Cranial nerves relay information between the brain and parts of the body, primarily to and from regions of the head and neck, including the special senses of vision, taste, smell, and hearing.
CN II = optic nerve, transmits visual information from the retina to the brain.
CN VII = facial nerve, controls the muscles of facial expressions
CN X = vagus nerve, interfaces with the parasympathetic control of the heart, lungs, and digestive tract

Question 12

Briefly describe the cerebellum, including;

1. what it connects to
2. what it is involved in

Answer 12

The cerebellum (little brain) attaches to the brainstem via 3 peduncles
The cerebellum plays an important role in motor control.
Maintains balance and control

Question 13

Describe the cerebrum of the brain

Answer 13

In the human brain, the cerebrum is the uppermost region of the central nervous system.
It is split into 4 lobes;
- frontal
- parietal
- temporal
- occipital
The cerebrum is also divided into the left and right cerebral hemispheres.
It is wrinkled with hillocks (gyri) and grooves (sulci).
With the assistance of the cerebellum, the cerebrum controls all voluntary actions in the human body.

Question 14

Name and describe the main sulci and gyri of the brain

Answer 14

The larger sulci are usually called fissures.
Central sulcus = groove between frontal and parietal lobes
Sylvian fissure = between temporal and frontal lobes
Central fissure = separates the 2 hemispheres

Question 15

Name the lobes of the cerebral cortex and what they are responsible for

Answer 15

Frontal = at the front
- responsible for movement, behaviour and emotion
Parietal = behind the frontal
- responsible for language, sensation and perception fo space
Occipital = at the back
- responsible for vision
Temporal = at the sides
- responsible for hearing, receptive speech and memory

Question 16

Briefly describe what the basal ganglia is.

Answer 16

The basal ganglia are neurons deep in the brain that are key to movement, perception, and judgment.

• striatum (caudate and putamen)
• globus pallidus
• substantia nigra
• subthalamic nucleus

Question 17

What are the 3 structures that protect the brain and what do they protect from?

Answer 17

• the meninges
• the cerebrospinal fluid
• the skull
  Protect the brain from contusion and infection

Question 18

Briefly describe the meninges

Answer 18

The 3 layered membrane that lines the skull and vertebral canal

• dura matter = outermost layer, thick and tough
• arachnoid matter = stretches between dura and pia matter. Helps keep the brain in place in the skull.
• pia matter = thin layer that follows the contours of the brain. Acts as a barrier and also aids in the production of CSF

Question 19

Briefly describe what CSF is and its role

Answer 19

Straw coloured viscous fluid produced in the lateral ventricles
Circulates around the brain and spinal cord in the subarachnoid space
It cushions the brain within the skull and serves as a shock absorber for the central nervous system
CSF also circulates nutrients and removes waste products from the brain.

Question 20

Describe the blood circulation of the brain

Answer 20

The brain is supplied with blood both anteriorely via internal carotid arteries and posteriorly via the vertebral arteries
To limit the possibility of loss of blood supply, the brain has evolved a circular vascular anatomy called the Circle of Willis

Question 21

What is a synapse and what occurs here?

Answer 21

A synapse is where one neuron meets and communicates with another
A chemical messenger (neurotransmitter) is released from one axon (presynaptic) and picked up by the dendrites of another (postsynaptic)

Question 22

Give an overview of how an action potential causes contraction of muscles

Answer 22

Motor neuron fires an AP down its axon
The axon terminal releases Ach into the synaptic cleft
Ach binds to the receptors on the junctional folds of the sarcolemma.
Ach binding causes a local depolarization called an end plate potential (EPP)
EPP triggers AP in adjacent sarcolemma
Sarcoplasmic reticulum releases Ca2+
Ca2+ binds to tropinin, which shifts tropomysoin to uncover the myosin-binding sites on actin.
Mysoin heads bind to actin
Contraction occurs via cross bridge cycling

Question 23

What causes an action potential?

Answer 23

Action potential is the result of a predictable sequence of electrical changes

Question 24

What is a refractory period in a muscle fiber?

Answer 24

During repolarization, a muscle fiber is said to be in a refractory period, because the cell cannot be stimulated again until repolarization is complete

Question 25

Describe the build up of a motor neuron

Answer 25

Each neuron has a long threadlike extension called an axon that extends from the cell body in the spinal cord to the muscle fiber. It divides at the fiber, giving off several branches that collectively form a neuromuscular junction or motor end plate. The end of the axon (axon terminal) and muscle fiber are separated by a space (synaptic cleft). Within the axon terminal are synaptic vesicles (small membranous sacs containing the neurotransmitter Acetylcholine Ach).

Question 26

Describe how an end plate potential is made

Answer 26

AP arrives at axon terminal
Voltage gated Ca2+ channels open and Ca2+ enters the axon terminal reducing the electrochemical gradient
Ca2+ entry causes Ach to be released by exocytosis
Ach diffuses across the synaptic cleft and binds to Ach receptors on the sarcolemma
Ach binding opens chemically gated ion channels, that allow Na+ into the muscle fiber and K+ out of the muscle fiber. More Na+ ions enter, producing a change in the membrane potential (end plate potential)

Question 27

Describe the 3 steps of triggering and then propogating an action potential

Answer 27

1. Generation of EPP
   EPP is generated in the neuromuscular junction and causes a wave of depolarization that spreads to the adjacent sarcolemma
2. AP depolarization
   Depolarization of the sarcolemma opens voltage-gated Na+ channels. Na+ enters, down its electrochemical gradient. At a certain membrane voltagen an AP is generated which propagates along the sarcolemma in all directions
3. AP repolarization
   Voltage-gated Na+ channels close and voltage-gated K+ channels open. K+ diffuses put of the muscle fiber, down its electrochemical gradient and restores the negatively charged conditions of the sarcolemma.