Tissues 6- Nerves

Question 1

What are the sections of the cerebral hemisphere

Answer 1

Frontal - front

Occipital - back

Temporal - side
Sound and speech recognition

Parietal - middle top
Sensory and motor function (proprioception)

Question 2

Parts of the brainstem

Answer 2

Descending Order:
Midbrain
Pons
Medulla

Question 3

Describe the cerebellum

Answer 3

Hindbrain structure attached to the brainstem

Important in fine-tuning motor function

Involved in balance and posture

You can exist without the cerebellum but life will be more difficult

Question 4

Describe the spinal cord

Answer 4

Extends down from the medulla in the brain stem

Conduit for neural transmission

Co-ordinates some reflex actions

Question 5

Describe unipolar, psuedo-unipolar, bipolar and multipolar cell types of the nervous system

Answer 5

Cells of the Nervous System

Unipolar
Has a cell body and one axon in one direction.
Rarely found in the CNS
Mainly found around the retina.

Pseudo-unipolar
Single axonal projection which splits into two
Rarely found in the CNS
Mainly found in the pain pathway in the PNS

Bipolar
Two projections from the cell body
Rarely found in the CNS

Multipolar - COMMON
Numerous projections coming from the cell body
ONLY ONE AXON - the rest are dendrites
Multipolar neuronal cells can have many morphologies
Pyramidal Cells - pyramid shaped cell body
Purkinje Cells - GABA neurones found in the cerebellum
Golgi Cells - GABA neurones found in the cerebellum

Question 6

Describe Neurones, name some common features (4) describe the axon and dendrites

Answer 6

Excitable cells - ability to change their membrane potential and send action potentials along their axon.
Heterogenous Morphology - lots of different types of cells
Non-dividing cells

Common Features: 
Soma (cell body, perikaryon) 
Nucleus and Ribosomes 
Protein production 
Neurofilaments - type of intermediate filament provides structural support and transport 

Axon 
It's a multipolar cell but only have ONE AXON 
Originates from soma at axon hillock 
Can branch off into collaterals 
Myelinated 

Dendrites
NOT MYELINATED
Receive information

Question 7

Describe astrocytes (4)

Answer 7

Structural cells - support by acting as a ‘glue’

Repair - provide nutrients for repair of neuronal cells

Facultative Macrophages - can turn into macrophages when necessary

Homeostasis - mop up neurotransmitter and other substances that are released within the CNS - sort of like a sponge

Question 8

Describe Oligodendrocytes (2) and Schwann Cells (2)

Answer 8

oligodendrocytes
Make myelin for the CNS
One oligodendrocytes myleinate many axons

Schwann Cells
Produces myelin for peripheral nerves (PNS)
ONE SCHWANN CELL MYELINATES ONE AXON SEGMENT

Question 9

Microglial (2) and Ependymal Cells (2)

Answer 9

Microglial Cells
Immune cells of the CNS
Similar to macrophages

Ependymal Cells
Epithelial Cells of the CNS
Line fluid filled ventricles - full of cerebrospinal fluid
Regulate production and movement of cerebrospinal fluid

Question 10

Describe an action potential

Answer 10

There is normally high sodium outside and high potassium inside.

When membrane potential changes from -70mV to around -40mV the VGSC opens leading to influx of Na+.

This causes a rise in membrane potential (depolarisation)

Then the VGKC opens and you get efflux of K+ - repolarisation

Membrane returns to resting potential

Sodium-Potassium pump restores membrane potential.

Question 11

What is saltatory conduction

Answer 11

If there was no myelination - you get slow movement of action potentials along the axon via cable transmission

Myelin prevents the action potential from spreading because it has high resistance and low capacitance

Nodes of Ranvier have a dense concentration of VGSCs and VGKCs

Action Potentials jump between Nodes of Ranvier allowing faster conduction.