The nervous system

What is the difference between graded and action potentials?

Graded=short distance in small regions of plasma membrane, magnitude of pot. diff. can vary, no threshold or refractory period

Action=long distance with large alterations in membrane potential, all or nothing law (fixed amplitude), threshold and refractory period

How can a graded potential be decremental?

Ions will leak out of membrane

Action potential mechanism

1)  -70mV

Typical threshold stimuli requirements

15mV less negative than resting membrane potential

Structure of an axon

Glial cells

90% of CNS - provide physical and metabolic support to soma, axon and dendrite 

What is a group of axons together in the CNS called?

Pathway/tract

Group of axons that links right and left of CNS

Commissure

Cell bodies of neurons with similar functions in PNS

Ganglia

Cell bodies with similar functions in the CNS

Nuclei

3 main regions of brain

Forebrain, Brainstem, Cerebellum

4 lobes to forebrain

Frontal, Parietal, Occipital, Temporal

What are dendritic spines?

Protrusions that increase surface area and contain ribosomes

Name a difference between making of myelin in CNS and PNS

• in CNS myelin made by oligodendrocytes whereas in PNS by Schwann cells

What is anterograde movement and which protein is responsible for this movement?

Kinesins aid movement from cell body to axon terminals e.g. nutrients, neurotransmitter, filled vesicles

What is retrograde movement and which protein is responsible?

Dyneins control movement from axon terminals to cell body e.g. recycles membrane vesicles, growth factors

What are the three functional classes of neurons?

1) Afferent neurons: from PNS (tissues) to CNS
2) Efferent neurons: from CNS to effector cells

3) Interneurons: within CNS (>99% of all neurons)

What is the composition of cell types in the CNS?

Neurons: 10% of cell types (but take 50% of space)

Glial cells: 90% (remainder)

Give 3 examples of glial cells

1) Astrocyte → regulates K+ and neurotransmitters in extracellular fluid/ form blood brain barrier by stimulating epithelial cells to form tight junctions

2) Microglial cells → specialised macrophage like cells

3) Ependymal cells → found in fluid filled cavities and regulate flow of cerebrospinal fluid

What are gyri and sulci

What is the outer cerebral cortex and inner cerebral cortex made of?

Outer = grey matter (interneurons, cell bodies, axons, glial)

Inner = white matter (myelinated fiber tracks)

What are the two components of the forebrain?

Cerebrum (two hemispheres) and diencephalon (central core)

What is the corpus callosum?

Massive bundle of nerve fibers connecting each cortex division

What are the two types of cells in the cerebral cortex?

Pyramidal → major output/ excitation

Non-pyramidal → major input/ receive signals

What are the 3 regions of the diencephalon?

1) Thalamus: movement, attention, arousal

2) Hypothalamus: homeostatic regulation of internal environment

3) Epithalamus: controls biological rhythms via pineal gland

What is the role of the cerebellum?

Coordinates movement e.g. posture and balance through basal nuclei

What is the role of the brainstem?

Integrates input from all regions of CNS:

• motor functions

• cardiovascular, respiratory control, swallowing

• regulates sleep, wakefulness, attention, eye movement

• ESSENTIAL FOR LIFE

What are 3 types of meninges and what is their role?

Dura mater, Arachnoid mater, Pia mater are protective membranes around the CNS

What is the blood brain barrier?

A protective mechanism that helps to maintain a stable environment for the brain

Where to afferent and efferent fibers enter and exit from?

Afferent → dorsal root

Efferent → ventral root

How many pairs of nerves do we have?

43 (12 cranial, 31 spinal) found in:

• cervical

• thoracic

• lumbar

• sacral

• coccygeal

What are 3 components of brain stem?

Midbrain, pons, medulla oblongata

What are the two divisions of the PNS?

Somatic (voluntary) and autonomic (sympathetic/ parasympathetic)