Test 3 - Motion, Sleep, Feeding Review Flashcards
What is a sarcomere?
the contracile unit of a muscle
What makes up a sarcomere?
actin (thin filaments) and myosin (thick filaments)
How does a sarcomere contract?
- action potential down motor neuron leads to Ach release
- Ionotropic Ach receptor on skeletal muscle cell receives Ach
- Na+ enters and depolarization
- After depolarization, ion channels open in sarcoplasmic reticulum (propagation into T tubules)
- Ca is released and goes down the concentration gradient
- Tropoin binds to Ca
- Tropomyosin is released and actin is available
- Myosin heads slide on actin filaments which leads to muscle contraction
Motor unit
motor neuron and the muscle fibers it innervates (motor pool + motor pool)
Motor pools
cluster of motor neurons that innervate the same muscle (ventral spinal cord/brainstem)
How are motor pools and units used in a particular motion using antagonistic muscle pairs?
The knee jerk reflex - perform oppostie actions and often fire in succesion (in order for motor pool A to be excited the Pool B is inhibited by interneuron)
What are the motor cortex’s roles in motion?
- command center to initiate voluntary movement
- integrate info from multiple sensory systems
- send descending axons to motor control regions of brainstem, spinal cord interneurons, and motor neurons
What is the brainstem’s role in motion?
- motor control starts here
- mesencephalic locomotor region (MLR) initiates locomotion
What is the cerebellums role in motion?
fine control of movement and motor learning
How does the cerebellum control fine movement?
inferior olivary nucleus (glutamate) -> purkinje cells (GABA) -> deep cerebella nuclei
or
motor cortex -> pons (dopamine) -> granule cells -> parallel fibers (glutamate) -> purkinje fibers
Purkinjes are gabaergic and send info to vestibular nuclei
Extrapyramidal system
coordinating and processing motor commands at subconscious level
includes:
1. basal ganglia & assc. structures
2. subthalamic nucleus
3. substantia nigra
How do the striatum, substantia nigra, thalamus, and cortex regulate motion activity in brainstem.
Striatum receives info from cerebral motor cortex and sends it in two different pathways (direct & indirect)
pathways dependent on dopamine - can turn on striatum with dopamine from dopamine neurons which increase GABA signaling - in otherwords dopamine modulates excitatory synaptic connections b/w cerebral cortex and thalamus
Direct D1 Pathway
D1 of Striatum -> globus pallidus internal (GABA) -> brainstem)
Indirect D2 Pathway
D2 of Striatum -> globus pallidus external (GABA) -> STN (glutamate) -> GPI (GABA) -> brainstem
Another name for striatum
caudate putamen
Smooth muscle vs. skeletal muscle regulation:
smooth (cardiac & endocrine) is regulated by autonomic nervous system
skeletal is regulated by motor system = CNS (Ach) -> skeletal muscle
Sympathetic control
CNS (Ach) -> sympathetic ganglia of PNS (NE) -> smooth muscle
Parasympathetic control
CNS (Ach) -> parasympathetic ganglia of PNS (Ach) -> smooth muscle
ANS - prefrontal cortex
- awareness of how visceral organs feel
- sends to amygdala
- receives from insular cortex
ANS - amygdala
- emotion
- recieves from thalmus, insular cortex, and prefrontal cortex
- sends feedback to cortex, brainstem and hypothalamus
ANS - hypothalamus
- receives from amygdala
- sends to brainstem & preganglionic neurons
ANS - brainstem
- receives from hypothalamus and amygdala
- sends to preganglionic neurons
ANS - pre/post-ganglionic neurons
pre: innervate post-ganglionic
post: innervate affectors
ANS - insular cortex
- works with prefrontal to make cerebral control center of ANS
- receives from thalamus
- fx: taste, pain, sensation from internal organs
ANS - thalamus
- receives from parabrachial nucleus
- sends to insular & amygdala
ANS - parabrachial nucleus
info from NTS sends info through here from brainstem to thalamus
ANS - Nucelus of solitary tract (NTS)
collects sensory info from internal organs
ANS - visceral sensory neurons
transmit info via NTS
receive from effectors
Neuroendocrine system
collected parts of the nervous system that control the secretion of hormones to regulate physiology and behavior in response to sensory stimuli
What does the hypothalamus control?
- control energy expenditure (food, metabolism)
- BP & electrolytes
- reproduction
- body temp
- emergency response (symp. activation & stress hormones)
- circadian rhythm & sleep
What is the relationship between the hypothalamus and the pituitary gland?
hypothalamus is the control center for hormone secretions of the pituitary
Pituitary gland
the endocrine center of the brain
Hypothalamus to anterior pituitary
anterior pituitary receives pre-hormones excreted by hypothalamus via portal vessel
Hypothalamus to posterior pituitary
peptide hormones go directly into bloodstream via long axon
How does the hypothalamus regulate other organs?
- direct hormone release by hypothalamic neurons at the posterior pituitary
- stimulatory action of hypothalamic neurons on anterior pituitary endocrine cells
- inhibitory action of hypothalamic neurons on anterior pituitary endocrine cells
Hypothalamus and thyroid relationship
stimulation of anterior pituitary leads to thyrotropin-releasing hormone (TRH) sent from hypothalamus to pituitary and thyroid-stimulating hormone (TSH)/prolactin release in thyroid (metabolism & milk production)
What is leptin?
secreted hormone protein (coded by OB gene in mice) - negatively regulates intake through its actions on specific neurons in the brain
Where does leptin come from in the body?
adipose tissue
What does leptin do in the brain?
inhibition of eating
How does leptin inhibit eating in the brain? (1st pathway)
- leptin activates POMC neurons (leptin receptors) -> less GABA inhibition -> depolarize POMC
- POMC cleaved -> into the neuropetides d-MSH & MCHR
- appetite reduced with binding to neuropeptides
How does leptin inhibit eating in the brain? (2nd pathway)
- leptin inhibits AgRP neurons (appetite stimulators)
- inhibition of eating
How does sugar and fat lead to sugar addiction?
Leptin & insulin increase from food intake can activate the arcuate nucleus (ARC) and ventral tegmental area which once activated by insulin secretion makes dopamine which increases addiction risk
What happens to genes’ expression all over the body during the 24 hour day?
circadian rhythm
Circadian rhythm
self-sustained oscillations in organisms behavior, physiology, and biochemistry
Explain the relationship b/w CLOCK, BMAL, PERs, and CRYs:
PERs & CRYs dimerize and neg. regulate the transcription factors CLOCK & BMAL1 (which both affect Circadian rhythm output) - CLOCK & BMAL1 form a complex and bind to the promoter and activate transcription of PER & CRY which enter and neg. regulate the other other complex which stops their own production = a negative feedback loop
Light entrainment
circadian rhythm phases ability to be reset by light (i.e. recover from jetlag)
ipRGCs
intrinsically photosensitive RGCs - send light to suprachiasmatic nucleus (SCN)
What happens to ipRGCs in light?
light activates ipRGCs -> release glutamate on SCN of hypothalamus neurons -> Ca entry, kinase activation, and phosphorylation of CREB -> CREB tx factor for PVH (temp. control nucleus of hypothalamus)
What happens to ipRGCs in dark?
does not activate -> no glutamate sent -> something happens here -> pineal gland excitation -> makes melatonin
Suprachiasmatic nucleus of the hypothalamus
master regulator of light entrainment - circadian rhythm regulation (circadian pacemaker neurons)
Pineal gland in the dark
no glutame from ipRGCs -> SNC doesn’t inhibit PVH -> PVH is active & excites pineal gland -> melatonin secreted
