Neurons and the Brain

Question 1

What is part of the central nervous system?

Answer 1

Brain (forebrain, midbrain, hindbrain) and spinal cord

Question 2

What is part of the peripheral nervous system? (structures)

Answer 2

Cranial nerves, spinal nerves, peripheral ganglia (cell bodies in periphery)

Question 3

What are the two large divisions of the peripheral nervous system? And the divisions that fall below?

Answer 3

Somatic (conscious control): contains the motor (muscle control) and sensory (aware of senses, 5 main ones)
Autonomic (visceral, unconscious control): motor system like heart beating (sympathetic and parasympathetic) and sensory (sensations from guts)

Question 4

What is the two motor divisions of the autonomic nervous system?

Answer 4

Sympathetic: fight/flight, HR/BP increase, pupils dilate, glands shut down, bronchi dilate to get more O2
Parasympathetic: rest/digest, HR/BP decrease, pupils normal, bronchi constrict back to normal

Question 5

What are the two cells in the nervous system?

Answer 5

Neurons: nerve cells that conduct signals
Neuroglia: support cells for the neurons

Question 6

What are some features of neurons (facts)? (2)

Answer 6

The brain has 100 million neurons
Neurons form connections to other cells via synapses (10^15 synapses, each neuron has about 100,000 connections with other neurons)

Question 7

What are the two types of nerve cell bodies?

Answer 7

Nucleus: collection of nerve cell bodies within the CNS
Ganglion: collection of nerve cell bodies within the PNS

Question 8

What are the structures of the neurons from dendrites to axon hillock?

Answer 8

Dendrites, cell body (contains the nucleus, nucleolus, Nissl bodies, mitochondria), neurofibrils provide structural support for axon hillock and axon hillock has the initial segment which makes decision if cell will fire an action potential

Question 9

What are the neurons structures below the axon hillock?

Answer 9

Axon: 1 per cell
Axon collateral: branches of the axon
Myelin sheath: insulator and increase speed
Schwann cells make myelin in PNS
Axon terminal
Synaptic bouton

Question 10

What are the three types of inputs that come from the Initial segment?

Answer 10

Excitatory input
Inhibitory input
And then the summation of both into the threshold potential and the cell fires

Question 11

What are the three different classes of neurons?

Answer 11

Multipolar: normal neuron, multiple projections from one cell body
Unipolar: 1 appendage from cell body, usually sensory\
Bipolar: 2 appendages from cell body, RARE, found in special senses (5 senses)

Question 12

What are the two other types of special neurons/cells?

Answer 12

Pyramidal cell: predominant cell type in cerebral cortex
Purkinje cell: cerebellum, complex dendritic tree because compares what you want to do and what you are doing, controls and corrects motion (move smooth)

Question 13

What are the two types of neuroglia found in the PNS?

Answer 13

Satellite cells: surround neuron cell bodies in ganglia, regulate O2, CO2, nutrient and NT levels around neurons in ganglia
Schwann cells: surround all axons in the PNS, responsible for myelination of PNS axons, participate in repair process after injury

Question 14

What are the four types of neuroglia found in the CNS?

Answer 14

1. Oligodendrocytes: myelinate CNS, provide structure framework, filipodium attach one ODC to many axons
2. Astrocytes: maintain BBB, structural support, regulate nutrient and dissolved gas, absorb and recycle NT, form scar
   (reactive astrocytes help with spinal cord damage to form scar tissue but this means new axons cannot grow and repair)
3. Microglia: remove cell debris, wastes and pathogens by phagocytosis
4. Ependymal cells: line ventricles and central canal, assist producing, circulating, and monitoring of CSF

Question 15

What are the two structures that protect the CNS?

Answer 15

Meninges: cover and protect the CNS
- Dura mater: tough outer layer
- Arachnoid mater: CSF
- Pia mater: intimate contact with brain, cannot peel it off
CNS floats in cerebrospinal fluid (cushioning during accel)

Question 16

What are the brain layers starting at the scalp?

Answer 16

Scalp, pericranium (connective tissue), calvaria (skull cap), dura mater, arachnoid mater, pia mater, brain

Question 17

What does the arachnoid layer look like?

Answer 17

Sarrann wrap with blood vessels

Question 18

What are the three main parts of the brain?

Answer 18

Cerebrum (shaped like a bum)
Cerebellum (shaped like a bell)
Brain stem (shaped like a stem)

Question 19

What are the 5 functions of the cerebrum?

Answer 19

Higher cognitive functions (thought, intellect, planning, creativity)
Language and speech (formulation and comprehension)
Somatic motor function (regulates skeletal activity and coordinates movement through BG)
Somatic sensory function (interpret stimuli from the environment)
Regulates the emotional aspects of behaviour

Question 20

What is the structure of the cerebrum?

Answer 20

2 hemispheres, 4 lobes, 3 poles, 3 major grooves, many sulci and gyri
Cerebral cortex: grey matter (neuronal cell bodies)
Cerebral medulla: white matter (axons)

Question 21

What are the three major grooves, 4 lobes, 2 hemis, and 3 poles in the cerebrum?

Answer 21

Hemis: left and right
Poles: frontal, temporal (x2), occipital
Grooves: longitudinal fissure, central sulcus, lateral sulcus
Lobes: frontal, occipital, parietal, temporal

Question 22

What are the roles of the 4 lobes of the brain?

Answer 22

Frontal: higher cognitive, planning, strategy, motor
Parietal: perception of self in space, sensory
Temporal: memory, learning, social, hearing
Occipital: vision

Question 23

What are the two gyri that line the central sulcus?

Answer 23

Precentral gyrus: primary motor cortex (frontal)
Postcentral gyrus: primary somatosensory cortex (parietal)

Question 24

What is the motor homunculus? How many are there?

Answer 24

2, one in each hemisphere
Exists in the precentral gyrus (primary motor)
Lots of cortex devoted to hand (upper extremity) because lots of control in movement, same with face
Representation of body parts with more cortex dedicated to them

Question 25

What is the sensory homunculus? How many are there?

Answer 25

2, one in each hemisphere Exists in postcentral gyrus (primary sensory) Representation of the amount of cortex dedicated to sensory movements Lots in face and hands

Question 26

What is the reason why no organs are represented in the sensory homunculus?

Answer 26

NO ORGANS (visceral structures): innervated by spinal cord levels, sensory info to brain in form of spinal cord levels therefore pain manifests in the body areas that are also linked to those spinal cord levels (pain in body wall)

Question 27

What is contained in the grey and white matter?

Answer 27

Grey matter: in cortical region, cell bodies White matter: in medulla, myelinated axons due to phospholipids (FAT) that are white

Question 28

What are the three types of fibre tracts in the brain?

Answer 28

Projection fibres: travel to and from cortex (sense, motor) Association fibres: intrahemi connections, short OR long, can be within lobe or between lobes (Broca's/Wernicke's) Commissural fibres: interhemi connections between RT and LT, corpus callosum between them

Question 29

What are the 4 characteristics of the cerebellum?

Answer 29

Acts as a comparator: compares intended movement and evolving movement and corrects for errors Ensures movements are smooth, coordinated and purposeful (skilled) Regulates posture and balance Disease: cerebellar ataxia (intention tremor, lack of balance and coordination)

Question 30

What are the three structures in the brainstem?

Answer 30

Midbrain, pons, medulla oblongata (this also goes from highest to lowest)

Question 31

What structures lie above the midbrain?

Answer 31

Diencephalon (thalamus, hypothalamus)

Question 32

What are the 5 characteristics of the brainstem?

Answer 32

Contains motor/ sensory pathways connecting cerebral cortex and thalamus to spinal cord Houses cranial nerve nuclei (origins of the CNs) Contains the reticular activating system: important for arousal of cortex and consciousness Vital centers for regulating heart rate and breathing Centers for swallowing and gag reflex regulation

Question 33

What are the four things contained in the midbrain?

Answer 33

Substantia nigra: regulates motor activity, neuronal degeneration leads to Parkinsons Red nucleus: regulates motor activity Relay centers for visual and auditory pathways Cranial nerves III and IV attached to it

Question 34

What is contained within the pons?

Answer 34

Bridge between cerebrum and cerebellum Cranial nerves V, VI, VII, VIII attached to it

Question 35

What is contained within the medulla?

Answer 35

Contains vital cardio-respiratory regulatory centers Cranial nerves IX, X, XI, XII

Question 36

What are the 4 ventricles of the brain? How does the CSF get into the spine?

Answer 36

Lateral ventricles: in LT and RT hemispheres, have anterior horn in frontal lobe, posterior horn into occipital lobe and inferior horn into the temporal lobe Third ventricle: between thalamic lobes Fourth ventricle: between pons and cerebellum Gets into the spinal cord via the central canal Cannot see lateral ventricles because deep in the brain

Question 37

What are the 3 cerebral arteries and what do they feed?

Answer 37

Anterior cerebral artery: midsagittal surface supply Middle cerebral artery: ICA moves here, lateral blood supply Posterior cerebral artery: posterior blood supply

Question 38

What does the basilar artery and vertebral artery do?

Answer 38

Basilar artery: anterior to pons, bifurcates into LT/RT posterior cerebral artery Vertebral artery: posterior blood supply enter by foramen magnum and form basilar

Question 39

What do the two communicating arteries do?

Answer 39

Posterior communicating artery: LT/RT between posterior and middle cerebral artery Anterior communicating artery: between 2 anterior cerebral

Question 40

What is the Circle of Willis?

Answer 40

Circle of blood vessels around the base of the brain therefore shunting blood from one place to another during injury