02 Endocrine Flashcards
What is the CNS comprised of?
brain and spinal cord
What is the PNS comprised of?
cranial nerves, spinal nerves, ganglia, peripheral nerves
What are the two types of neurons that connect the periphery with the CNS?
- motor (efferent) neruons
- sensory (afferent) neurons
What are the two divisions of motor (efferent) neurons?
- somatic - voluntary
- autonomic - involuntary - (divided into sympathetic and parasympathetic NS)
What forms myelin in the peripheral nervous system?
schwann cells
Describe how an AP travels down a presynaptic neuron and the response it elicits in the postsynaptic neuron
- AP arrives at presynaptic axon terminal
- voltage gated Ca+ channels open resulting in Ca2+ influx into the presynaptic membrane
- synaptic vessels fuse to presynaptic membrane and expel neurotransmitter (NT) into synaptic cleft
- NT diffuses across synaptic cleft
- NT binds to receptors on postsynaptic membrane
- ligand gated ion channels open resulting Na+ influx
- Postsynaptic potential depolarizes to threshold triggering an AP
What is the sensory input for autonomic and somatic systems?
- Autonomic - interoreceptors
- Somatic - special senses and somatic senses
What neurotransmitters are present in the autonomic vs somatic system?
- autonomic - acetylcholine and norepinephrine
- somatic - acetylcholine
Where is ACh released in the autonomic system?
- preganglionic axons
- postganglionic parasympathetic
- postganglionic sympathetic to sweat glands
Where is norepinephrine released in the sympathetic system?
postganglionic sympathetic fibres other than to sweat glands
The motor neuron pathway of the somatic vs autonomic system consist of a _____# neuron pathway
- somatic - one neuron
- autonomic - two neuron
What are the effectors in the somatic system?
skeletal muscle
What are the effectors in the autonomic system?
cardiac muscle, smooth muscle, and glands
Describe the neuron pathway and the neurotransmitter involved in the somatic NS
One neuron pathway, myelinated, releases ACh, effector is skeletal muscle
Describe the neuron pathway and the neurotransmitters involved in the parasympathetic NS
two neurons pathway, preganglionic neuron is myelinated, synapses in the autonomic ganglion, releases ACh, 2 neuron (postganglionic neuron) is unmyelinated and releases ACh
What is ganglion and where is it found?
neuronal bodies found in the somatic and autonomic branches of the PNS
What is the function of the hypothalamus?
- controls internal organs via the autonomic nervous system and pituitary gland
- regulates behavioral patterns, circadian rhythm, body temperature and eating/drinking behaviour
What three glands influence other glands?
hypothalamus, pituitary and adrenal glands
Describe the order of actions lipid soluble hormones take to act on target cells
- transported in blood bound to transport proteins
- diffuse directly through cell plasma membrane
- bind to receptors within nucleus or cytosol of a target cell to alter gene expression
- mRNA direct synthesis of new proteins (usually enzymes)
- physiological responses/cell activity altered response to the hormone
Describe the order of actions water soluble hormones take to act on target cells
- binds to receptors on target cell membrane
- activates G protein which activates adenylate cyclase
- ATP converted to cAMP.
- cAMP activates protein kinases
- phosphorylation of enzymes within the cell
With respect to size and myelination of cell axons, the velocity of nerve impulse conduction is greatest in what size and myelinated or non myelinated fibres?
large diameter, heavily myelinated fibres
Endocrine hormones act on ____ cells
distant target
Paracrine hormones act on ____ cells
local target
Autocrine hormones act on ________
- the cell that produced the hormone
The neurotransmitter released from the sympathetic preganglionic neuron is
acetylcholine
The neurotransmitter released from the the sympathetic postganglionic neuron on most effector tissues is
norepinephrine
the neurotransmitter released from the sympathetic postganglionic neuron on sweat glands is
acetylcholine
The neurotransmitter released from the parasympathetic preganglionic neuron is
acetylcholine
the neurotransmitter released from the parasympathetic postganglionic neruon is
acetylcholine
What is the difference between preganglionic and postganglionic neurons?
preganglionic neurons arise from the central nervous system and supply the ganglia
postganglionic neurons arise from the ganglia and supply the tissues.
What are interoceptors?
a sensory receptor which receives stimuli from within the body
The sensory input for the somatic nervous system is ___?
special senses and somatic senses
The sensory input for the autonomic nervous system is ___?
interoceptors
The control output is voluntray/involuntary for the somatic nervous system
voluntary
The control output for the autonomic nervous system is voluntary/involuntary ?
involuntary
The motor neuron pathway of the somatic nervous system consists of a one/two neuron pathway?
one neuron
The autonomic nervous system consists of a one/two neuron pathway?
two neuron
How is the anterior pituitary gland connected to the hypothalamus?
connects to the hypothalamus bia the hypophyseal portal system (vascular connection)
What is the name of the stalk that connect the hypothalamus and the pituitary gland?
infundibulum
What is the function of the anterior pituitary gland?
responds to releasing and inhibiting hormones from ventral hypothalamus (GHRH, GHIH, TRH, CRH, GnRH, PIH)
releases GH, TSH, ACTH, FSH, LH, PRL
How does the posterior pituitary gland connect to the hypothalamus?
Via the hypothalamic-hypophyseal tract (neural connection)
What is the function of the posterior pituitary gland?
responds directly to hypothalamic neurons?
releases oxytocin + ADH
What are the three components of an alarm response?
- alarm response
- extended alarm response
- resistance reaction
What division of the nervous system is involved in the alarm response?
sympathetic
What hormones mediate the extended alarm response? And which gland secretes these?
epinephrine, norepinephrine
secreted by the adrenal medulla
What hormone mediates the resistance reaction? What gland secretes this hormone?
cortisol
adrenal cortex
How long does the alarm response take?
milliseconds
How long does the extended alarm response take?
seconds - minutes
How long does the resistance response take?
minutes - hours
Describe the alarm and extended alarm response pathway
- sympathetic nerves (postganglionic norepinephrine) to visceral effectors (lungs, heart, blood vessels)
- flight or fight response elicited
and
- adrenal medulla secretes epinephrine and norepinephrine into blood
- supplements and prolongs the alarm response
Describe the resistance reaction pathway
- neurosecretory cells release CRH into primary hypophyseal plexus, then portal vein to anterior pituitary
- anterior pituitary releases ACTH into bloodstream
- adrenal cortex releases cortisol into the bloodstream
- resistance reaction elicited
Describe how the resistance reaction is regulated
- high levels of cortisol in the blood stream remain after stressor is removed
- inhibition of ACTH
- inhibits CRH secretion
Name some physiological responses of the alarm response
- Increased sweat gland secretion (cold sweat)
- Dilation of bronchi
- Dilation of pupils
- Heart: increased rate + force of contraction; “pounding heart”
- Skin: contraction of arrector pili in skin (goose flesh)
- Digestion: decreased salivation & digestion
- Constriction of peripheral blood vessels (pale skin)
- Increased blood pressure and water retention
Name some physiological responses of the resistance reaction
- Suppression of immune system
- Gluconeogenesis, lypolysis, AA breakdown
- Resistance to stresses eg. exercise, infection, trauma
- Reduced inflammation/anti-inflammatory
- Sensitised vessels (to agents that cause vasoconstriction)
