Lecture 5: Autonomic and Endocrine systems Flashcards
Describe the physical division of the nervous system and the structures involved in each division
It is split into a CNS and PNS. CNS is made of the brain and spinal cord. PNS includes all nervous tissue outside CNS including spinal nerves, cranial nerves, Ganglia and peripheral nerves
Describe the functional division of the nervous system as a whole
The CNS responds to incoming sensory information (afferent neurons) from PNS. It sends motor (efferent neurons) through cranial and spinal nerves to PNS. PNS is divided into the Somatic NS, Autonomic NS and Enteric NS.
Compare the SNS and ANS in terms of sensory input, control of output, motor neuron pathway, neurotransmitters and effectors
- SNS inputs special sensory information and normal somatic senses. Whereas ANS uses interoceptors in visceral organs monitoring internal conditions that are less consciously felt.
- SNS is under voluntary motor control from cerebral cortex whereas ANS is involuntary from the limbic system, hypothalamus, brainstem and spinal cord.
- SNS has a specific one neuron pathway, whereas ANS has 2 neuron pathway that is more simultaneous.
- SNS uses ACh only for excitement, whereas ANS uses ACh and Norepinephrine depending on the division. - – SNS Effector tissue is skeletal muscle whereas ANS effector tissues are smooth muscle, cardiac muscle and glands. Both are innervated by CNS
Describe the Enteric nervous system- sensory receptors, effector tissues - under involuntary control
Sensory neurons monitor chemical changes in GI tract as well as wall stretching. Enteric motor neurons are in Enteric plexuses communicate with CNS through ANS but generally independent. They govern contractions, secretions and activities of endocrine cells in effector tissue (smooth muscle, glands and endocrine cells of GI tract).
What is the broad purpose of the Nervous System
A system of communication to allow us to coordinate our actions and bodily functions to adapt to a changing environment. Sensory, integrative and Motor.
Describe the features of transmission of impulses from one nerve to another (synapse)
Dendrites have numerous receptor sites for binding chemical messengers from other cells. AP travels from the cell body down the long axon to the synaptic end bulb of axon terminals. This causes a change in shape in voltage gated Ca2+ channels allowing Ca2+ to enter. Ca2+ causes synaptic vesicles containing neurotransmitter to fuse with the cell membrane so it can cross the synaptic cleft and bind to ligand gated ion channel on the post synaptic neuron. This makes a shape change that allows Na+ to enter the post synaptic neuron and depolarise-> AP.
What is the difference between myelinated and unmyelinated nerve fibres in the PNS
Both axons are covered by Schwann cells however for myelinated, One schwann cell can produce the myelin sheath for one axon by spiralling many times around the axon- the glial membrane layers becoming the myelin.Bbut in unmyelinated On Schwann cell can enclose 20 or more unmyelinated axons
What are the neurotransmitters associated with the sympathetic and parasympathetic divisions respectively
Sympathetic and Parasympathetic divisions use ACh for the first synapse between the preganglionic neuron and postganglionic neuron at the ganglion, however for Sympathetic division to most effector tissues it uses Norepinephrine whereas Parasympathetic uses ACh. There is an exception in Sympathetic where sweat glands also use ACh
What are the features of the alarm response and which division is responsible for it
Sympathetic induces the alarm response: exercise, emotion and excitement. This causes
- Increased rate of contraction of heart, constriction of vessels , esp in skin-> increased blood pressure - can send nutrients where its needed
- Water retention - preserve body fluid volume in case of bleeding.
- Dilation of pupils (more aware)
- Decreased salivation, digestion
- Dilation of bronchi- more oxygen, breathe faster
- increased blood sugar
- contraction of arrector pilli muscles and increased sweat.
What are the features of the relaxation response and which division is responsible for it
Parasympathetic division induces relaxation response: repletion, rest and relaxation.
- Decreased rate and force of contraction
- Contraction of pupils
- Increased salivation, digestion
- Constriction of bronchi- slower breathing
- Dilation of peripheral blood vessels- more blood to peripheries- warmth.
Describe the locations of endocrine glands in the body
- in the brain: Hypothalamus (triangle under thalamus), pineal and Pituitary glands
- in the thoraic cavity: Thyroid on the trachea, Thymus on the heart
- in the abdominal cavity: Liver on top right, Adrenal glands on the top of the kidneys
- in the pelvic area: testes and ovaries
Compare function/ location of circulating hormones vs local hormones
Circulating hormones are made by endocrine cells which produce hormone which circulates in blood to reach distant target cells through capillaries - can linger. Whereas Local hormones are inactivated quickly, Paracrine cells act on neighbouring cells and Autocrines act on the same cell.
Describe the control of hormone release - how is it an inducible system
First the organ is triggered to synthesise, store and release hormone only when needed. Then it circulates in the blood and reaches target tissues. It will only induce a response if the target tissues have the correct receptor. As part of response, target tissues can release something that is detected by the organ as a negative feedback signal to switch off the production of the hormone. As the hormone is circulating, it also has breakdown or excretion to turn it off as well.
Describe the transport for Lipid soluble hormones (steroid and thyroid hormones) in the blood vs Water soluble
Lipid soluble hormones are bound to a transport protein made by the liver. They temporarily increase the solubility of the LSh in blood. Retard the passage of small hormones through filtering mechanism of the kidney therefore reduce loss in urine. Provide a ready reserve of hormone in the blood stream releasing a small fraction of hormones to be free when needed.
Watersoluble are just in free form.
Describe the mechanism of Action of Lipid soluble hormones
- LSh diffuses through blood, interstitial fluid into the cell to the nucleus
- hormone binds to receptors located within cytosol or nucleus. The activated receptor hormone complex then alters gene expression; turning genes on or off.
- newly formed mRNA directs synthesis of specific proteins on ribosomes. (enzymes possibly)
- New protein alters cell activity and causes response typical of that hormone.
