Autonomic and Endocrine Systems
Describe the structure of the nervous system and features of transmission of impulses from
one nerve to another
Synaptic transmission steps
1. Action potential arrives at pre-synaptic axon terminal
2. Voltage-gated Ca2+ channels open letting influx of Ca2+ into presynaptic membrane
3. Synaptic vescicles fuse with pre-synaptic membrane and expel neurotransmitter (NT) into synaptic cleft
4. NT diffuses across synaptic cleft and binds to receptors on post-synaptic membrane
5. Ligand-gated ion channels open so that there's an influx of Na+
6. Post-synaptic membrane depolarises to the threshold triggering an action potential
Veloctity of nerve impulse conduction is greatest in large diameter heavily myelinated fibres
Somatic nervous system
Autonomic nervous system
Regulates involuntary processes (heart rate)
Two neuron pathway
Control of output is voluntary
One neuron pathway
Neurotransmitters used are acetylcholine
Control of body movements via skeletal muscles
Neurotransmitters used are acetylcholine, norepinephrine and epinephrine
Acetylcholine is used for all preganglionic axons, postganglionic parasympathetic neurons and postganglionic sympathetic neurons to sweat glands
Norepinephrine is used for all postganglionic sympathetic neurons to effector tissues
Sensory input is special senses and somatic senses
Sensory input is interoceptors
Effectors are glands, cardiac muscle and smooth muscle
Effector is skeletal muscle
Sympathetic nervous system
Parasympathetic nervous system
Fight or flight
Rest and relaxation
Increased heart rate and contraction force
Dilation of pupils and bronchi
Increased sweating
Increased blood pressure, blood sugar, and water retention
Decreased heart rate and contraction force
Contraction of pupils
Bronchi constriction
Dilation of peripheral blood vessels
Constriction of blood vessels
Increased digestion
Preganglionic neuron (myelinated)
Postganglionic neuron (unmyelinated)
Somatic motor neuron (myelinated)
Name two broad classes of hormones and explain how they interact with target cells
Circulating hormones
From endocrine glads
Target cells are far away, so hormonees travel through blood stream to get to them
Local hormones
Paracrines target neighbouring or nearby cells
Autocrines target the cell that produced them; receptors are on the surface of the autocrine cell
General mechanisms of hormone action based on their chemical solubility
Lipid-soluble hormones
Steroid and thyroid hormones
Can pass through cell membrane so receptors are inside the cell (eg on the nucleus)
Water-soluble hormones
Peptides, proteins,
Cannot pass through cell membrane (hydrophobic inside bilayer) so receptors are on the cell membrane
Activates a series of enzyme controlled reactions inside the cell
Relationship between the hypothalamus and pituitary glands
The hypothalamus makes hormones and stores them in the posterior pituitary, and sends a signal for the posterior pituitary to release them when needed
Pituitary gland is inferior to the hypothalamus
Hypophyseal portal system is a system of blood vessels that pass from the hypothalamus down the pituitary stalk to the anterior pituitary
Vessels for hormones to travel through from hypothalamus to posterior pituitary
Explain why stress affects immune function
Stress response
Sympathetic autonomic activation
Glucose and oxygen consumption
Alertness and activity
Reduce tissue damage
Ward off danger/flee
Resistance reaction
Slower and longer lasting
Cortisol production