This summery contains all the cases discussed during the course homeostasis and organ systems (BBS1002). During this course, the tutorial groups talked about the autonomic nervous system, heart, lungs, GI tract, kidneys, and acid-base regulation. In the cases the anatomy, histology and function of ...
Summery cases
BBS1002
Homeostasis and organ systems
By Kim Staats
1. Autonomic nervous system
2. Heart I
3. Heart II
4. Lungs I
5. Lungs II
6. GI tract I
7. GI tract II
8. Kidneys I
9. Kidneys II
10. Acid-Base regulation
,Case 1 Autonomic Nervous System
1. How is the nervous system organized?
Central nervous system (CNS):
CNS = Brain + spinal cord
• Brain = cerebrum (big part) + cerebellum + thalamus + hypothalamus + brainstem.
o Cerebrum = controls intelligence, memory, personality,
emotion, speech and ability to feel and move.
▪ Corpus callosum = linkage of right and left
hemispheres by nerve fibres.
o Thalamus = moves information to and from the lobes in
cerebrum, controls movement and memory.
o Hypothalamus = controls appetite, thirst and body
temperature and produces hormones that control the
release of other hormones in the pituitary gland.
o Brain stem = mid brain + pons + medulla. Important for
breathing, blood pressure and how the body reacts to danger.
• Spinal cord = carries messages to and from the brain. It contains nerve bundles and cells that
carry these messages. It is for adults 45 cm long.
, Nerve pairs in spinal cord (total 31 pairs):
o Cervical nerve pairs (8) = nerves starting in neck running to
face and head.
o Thoracic nerve pairs (12) = nerves in upper body extening to
chest, upper back and abdomen.
o Lumbar nerve pairs (5) = nerves in lower back running to legs
and feet.
o Sacral nerve pairs (5) = nerves in lower back extending to
pelvis.
Peripheral nervous system (PNS):
PNS = nerves + ganglion
Types of nerves:
• Afferent nerves = sensory nerves which carry messages from PNS to CNS.
• Efferent nerves = motor nerves which carry messages from the CNS to PNS.
• Mixed nerves = nerves with both afferent and efferent neurons.
Types of PNS:
• Autonomic nervous system = the part of the peripheral nervous system that regulates the
basic visceral processes needed for the maintenance of normal bodily functions.
Visceral reflexes = subconscious sensory signals from visceral organs entering the autonomic
ganglia, the brain stem or the hypothalamus and then return subconscious reflex responses
back to the visceral organs to control the activities.
Types of tissue: cardiac muscle, smooth muscle and glands.
The autonomic system consists of two major divisions: the sympathetic nervous system and
the parasympathetic nervous system. These often function in antagonistic ways.
o Sympathetic nervous system = “fight-or-flight”. Uses acetylcholine and
norepinephrine, although norepinephrine is what reaches the organ.
Preganglionic neuron releases acetylcholine, which binds to the nicotinic receptors
on the post-synaptic membrane of the postganglionic neuron, or to the hormone-
producing cells of the adrenal medulla.
▪ Postganglionic neuron will release norepinephrine into the synaptic cleft with
the target cell. The NE will bind to the 𝛼 and 𝛽 receptors -> fast.
▪ Adrenal medulla will release NE and epinephrine into blood stream -> slow.
Hormone used as described above: epinephrine.
Functions = e.g. digestion slows down, blood moves towards head & limbs, decreases
urine output, stimulates vasoconstriction.
Preganglionic motor neuron is short, postganglionic motor neuron is longer.
o Parasympathetic nervous system = “Rest and digest”. The parasympathetic nervous
system uses only acetylcholine.
Preganglionic neuron releases acetylcholine, which attaches to nicotinic receptors on
the receiving end of the postganglionic neuron.
The postganglionic neuron releases acetylcholine into the synaptic cleft with the
target cell, binding it to its muscarinic receptor.
No hormones are used in the parasympathetic nervous system.
Preganglionic motor neurons are long, postganglionic motor neurons are short.
, o A third division of the autonomic system, the enteric nervous system, consists of a
collection of neurons embedded within the wall of the gastrointestinal tract and its
derivatives. This system controls gastrointestinal motility and secretion.
• Somatic nervous system (SoNS) = voluntary nervous system. It consists of neurons that are
associated with skeletal or striated muscle fibres and influence voluntary movements of the
body. The motor neurons that innervate striated muscles form the somatic nervous system.
Functions:
o The SoNS contains both afferent nerves traveling towards the CNS and efferent
nerves responsible for sending signals from the CNS towards the rest of the body.
The brain and spinal cord process the input from a variety of sources and integrate
them before devising a response. This response determines the location and strength
of muscle contraction across different parts of the body. Therefore, the primary
function of the somatic nervous system is to connect the CNS with organs and
striated muscles in order to enable complex movements and behaviour.
o Additionally, the SoNS also mediates a subset of involuntary muscle responses called
reflex arcs. A reflex arc results in an extremely quick muscle contraction in response
to a stimulus, with minimal intervention from the brain. While the impulse for most
voluntary muscle contraction originates in the brain or brainstem, a reflex action can
be brought about with just a single sensory and motor neuron that synapse in the
spinal cord.
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