Quiz 9 - Spinal reflexes and reproductive systems Flashcards
4 functions of spinal reflexes
- Maintain walking movements
- Withdraw portions of the body from noxious stimuli
- Maintain tone in legs to maintain posture
- Regulate local blood vessels, GI movement, urinary excretion
Reflex Arc
“Local circuit”
Receptor –> Sensory Neuron –> Integration center –> Motor neuron –> Effector
What % of nerve fibers in spinal cord are propriospinal fibers?
50%
What are propriospinal fibers?
Fibers that connect segments of the spinal cord
What do sensory neurons do?
Respond to stimuli, either external or from CNS
What do muscle spindles do?
Provide information about muscle length to the CNS or spine based on how stretched out they are. Found within muscles. Increased stretch = increased firing rate
What do Golgi tendon organs do?
Provide information about tension placed on muscles, found in tendons. Increased stretch = increase firing rate
How many times more/less numerous are interneurons than motor neurons?
30X More numerous
What are Renshaw cells?
A type of interneuron that passes inhibitory signals to surrounding motor neurons to “sharpen” the signal
What is a motor unit?
Single motor neuron and the muscle cells it synapses
What do alpha motor neurons do?
Enervate larger skeletal muscle fibers
What do gamma motor neurons do?
Enervate intrafusal fibers of muscle spindles
What is a monosynaptic reflex?
Reflex whose circuits have no interneurons. Sensory synapses directly with motor.
Ex.) Muscle stretch reflex
What is a polysynaptic reflex?
Reflex that has interneurons between sensory and motor neurons, allowing modulation and more complex responses.
Ex.) Flexor-Extensor reflex
How does a stretch reflex work?
- Muscle spindle fiber responds to stretch of muscle
- Sensory neuron travels to spinal cord where it synapses with a motor neuron
- Motor neuron causes contraction of stretched muscle
- Sensory neuron can also synapse with interneuron to cause inhibition of opposing muscle motor neuron
What is the physiological purpose of a stretch reflex?
Maintain posture while walking or standing
What is the diagnostic test of the stretch reflex?
Knee jerk reaction
How do alpha and gamma motor neurons work together?
Both skeletal muscles and muscle spindles will contract or relax together to maintain ratio of muscle to muscle spindle length. This allows tone to be maintained during muscle movement.
How does a golgi tendon reflex work?
- Organ detects increased tension on tendon
- Sensory neuron travels to spinal cord, to interneuron
- Interneuron causes inibition of muscle of the stretched tendon and activation of opposing muscle
What is the physiological purpose of a golgi tendon reflex?
Ensure smooth voluntary movements at onset and termination of muscle contraction by equalizing contractile force.
Synchronizes force of contractile units, distributing load.
How does a flexor-extensor reflex work?
- Cutaneous sensory neuron interacts with multiple interneurons
- Interneurons cause activation and inhibition of motor neurons to cause affected limb to retract and opposite limb to push away.
What are the layers of the ovary from outside to inside?
Germinal epithelium - squamous or cuboidal
Tunica albugenia - dense connective tissue capsule
Cortex - contains follicles, highly cellular
Medulla - highly vascularized, pathways for estrogens and progesterone, loose CT
Follicular/Granulosa cells
Surround oocyte, secrete estrogen
What does estrogen do in the ovary?
Proliferate granulosa cells
Mature follicles
Monthly development of endometrium
What stimulates follicles to mature?
Estrogen and Follicle Stimulating Hormone (FSH)
What triggers ovulation?
Luteinizing Hormone (LH)
What are the steps of follicle development?
- Primary follicle: primordial follicle –> unilaminar primary follicle –> multilaminar primary follicle
- Secondary (Antral) follicle
- Graafian (mature) follicle
What is a primordial follicle?
Found in superficial cortex
Oocyte surrounded by simple squamous epithelium
Prophase of first meiotic division
What is a Unilaminar primary follicle?
Begin at beginning of puberty
FSH stimulates process of follicular growth
Oocyte surrounded by simple cuboidal epithelium
What is a multilaminar primary follicle?
Aka growing follicle
Follicular cells proliferate
Oocyte surrounded by stratified cuboidal epithelium (granulosa)
Zona pellucida appears between oocyte and first layer of granulosa cells (glycoprotein coat that initates acrosome reaction)
Interstitial cells differentiate into theca folliculi
What is a secondary (antral) follicle?
Granulosa cells accumulate liquor folliculi creating a fluid filled antrum
Granulosa cells convert androgens into estradiol via aromatase
Theca folliculi becomes 2 layers: theca interna (endocrine tissue that secretes androgens) and theca externa (CT and smooth muscle)
What is a Graafian (mature) follicle?
Oocyte surrounded by several layers of granulosa cells - corona radiata
Oocyte protrudes into antrum suspended by cumulus oophorus
Pre-ovulatory follicle
One dominant follicle will undergo ovulation per cycle.
What does initial surge of LH during ovulation do?
Oocyte in mature follicle completes first meiotic division
Granulosa cells produce prostaglandins/hyaluronan, ovarian wall weakens
Mature follicle ruptures and releases ovum together with corona radiata
What does the follicle become after ovulation?
Corpus luteum
What do granulosa and theca cells do under control of LH?
Granulosa lutein cells secrete progesterone and estrogen
Theca lutein cells secrete androgens and progesterone
What happens to corpus luteum if pregnancy doesn’t happen?
Degenerates after 14 days.
No LH, cells stop producing steriods
Decreased progesterone leads to menstruation
Corpus albicans - dense CT scar
What is atresia?
When follicles fail to mature and die
Most follicles die this way
In post-menopausal ovary, most follicles are gone due to ovulation or atresia
What collects oocyte into oviduct?
Fimbria
Where is the oocyte fertilized?
Oviduct
What are the layers of the oviduct?
Folded mucosa - simple ciliated columnar epithelium
Muscularis - circular and longitudinal smooth muscle
Serosa
NO SUBMUCOSA