Organ Systems

Question 1

Biological basis of behaviour I

Answer 1

*Somatosensation:
- position
- vibration
- touch
- pain
- temperature
*Muscle stretch reflex: causes a muscle to contract quickly after it is stretched
* gray matter has neuron somas and white matter has myelinated axons. Most of the gray matter of the spinal cord is inside and the white matter is outside. Most of the white matter of the brain is inside and the gray matter is mostly outside
*collections of axons are called tracts. The inner areas of gray matter are called nuclei

Question 2

Biological basis of behaviour II

Answer 2

Lower motor neurons control the skeletal muscles. Upper motor neurons control lower motor neurons. Their somas are in the cerebral cortex.
*corticospinal tract - from cerebral cortex to spinal cord to lower motor neurons in the spine; cross over to travel to other side of the body
*corticobulbar tract - upper motor neurons that work on lower motor neurons in the brain stem can work on the same side of the brain
*basal ganglia: motor, cognition, emotional
* thalamus: sensory, higher functions
*occipital is visual, parietal is somatosensory
*language mostly in the left cerebral hemisphere; right cerebral hemisphere tends to be in the right hemisphere mostly

Question 3

Neural cells I

Answer 3

Divided into neurons (transmit information) and glia (support neurons)
*astrocytes: central nervous system; highly branched; have end feet; they scaffold, form glial scars, homeoastasis, the blood brain barrier and clear synapses
*microglia: they’re small; come from the mesoderm; highly branched processes in every direction; become active upon inflammation; phagocytosis; antigen presentation
*ependymal cells: forms leaky barrier between interstitial and cerebrospinal fluids; secretes CSF
*oligodendrocytes: create myelin sheath around axons in the neurons of the CNS; influence neurons and glia through the exchange of materials
*schwann cells: glia of peripheral NS; from neural crest cells; produces myelin sheath from one segment of one axon; influence neurons through the exchange of materials

Question 4

Neuron membrane potentials 

Answer 4

• a synapse closer to the trigger zone has greater potential in terms of action potentials being fired
• K+, Na+, Cl-, and Ca2+ are most important for neurons. All except potassium are much more outside the cell than inside. Electrical forces like to move cations inside the cell and anions outside because the resting potential of the neuron is negative, but their diffusion forces will depend on their concentration gradients. Entry of chloride ions tend to be inhibitory, while entry of sodium and calcium tend to be excitatory.
• potentials decay with time and distance
• graded potentials vary based on the size of the stimulus. But action potentials are the same size for each neuron. They follow the all or nothing principle and don’t degrade with distance
• nodes of ranvier that are close to each other might cause action potentials to slow down; those that are far apart might cause it to stop
• axon diameter, not length affects conduction speed.

Question 5

Neural synapses

Answer 5

Neurotransmitters:
- amino acids e.g. glutamate, GABA, glycine
- peptides e.g. opioids (endorphin)
- monoamines / biogenic neurotransmitters e.g. histamine, serotonin ; include catecholamines e.g. dopamine, epinephrine, norepinephrine
- other e.g. acetylcholine

Ionotropic neurotransmitters receptor - ligand gated; graded potentials
Metabotropic neurotransmitter receptor - activate second messengers; slower than ionotropic

Neurotransmitter removal: diffusion, enzymes, repuptake pumps, astrocytes

Question 6

Type 1 and 2 muscle fibres

Answer 6

Type 1: Red (create more energy from oxygen; more mitochondria), slow, slow twitch, aerobic, long contractions, fatigue resistant, strong contractions, store energy as triglyceride

Type 2: white, fast, fast twitch, anaerobic, short contractions, easily fatigue, weaker contractions, store energy as ATP And creatine phosphates