PHYSIOLOGY Flashcards
what is the endometrium and what happens to it at the end of the menstrual period?
- layer of tissue lining the inside of the uterus
- the endometrium lining breaks down and leaves via the vagina (menstrual period)
how long is the average menstrual cycle, what day does ovulation usually occur?
- 28 days
- ovulation usually occurs at day 14
what is the pre-ovulatory period of the menstrual cycle called and what is the post-ovulatory period of the menstrual cycle called, and what hormones are at their highest in each of the phases?
- follicular phase (oestrogen at highest)
- luteal phase / secretory phase (progesterone at highest)
describe the process of the menstrual cycle (pre-ovulation, day 10-14, post-ovulation(up to day 15), after day 15)
PRE-OVULATION:
- hypothalamus releases gonadotropin-releasing hormone (GnRH)
- this stimulates the pituitary gland to release FSH and LH
DAY 10-14:
- positive feedback loop due to the follicle stimulating lots of oestrogen which acts on the pituitary gland making it more responsive to GnRH and therefore releases lots of FSH and LH
- this increase in FSH and LH occurs 1-2 days before ovulation and this stimulates ovulation
POST-OVULATION (up to day 15):
- increase in progesterone which acts as a negative feedback signal on the pituitary so less FSH and LH released
- also, inhibin is released by luteinised granulosa cells which inhibits FSH and LH production
- oestrogen levels decrease, progesterone increases
AFTER DAY 15:
- hormones are gradually stopped being produced
- oestrogen and progesterone levels decrease
- cervical mucus thickens (less hospitable for sperm)
- endometrium layer breaks down
when is the optimal chance for fertilisation period in the average menstrual cycle and what effect does an increase in oestrogen levels have on cervical mucus?
- day 11 to day 15
- increased oestrogen levels make the cervical mucus more hospitable for sperm
Describe in detail the physiological pathway of pain transmission from a joint to the brain
- Inflammatory markers (cytokines, histamine, prostaglandins etc.) released locally as a result of injury/inflammation
- Initial pain is sensed by nociceptors (free nerve endings in skin, muscle, other tissues)
- Pain is transmitted by primary sensory neurons to the dorsal horn of the spinal cord
- Type A-delta fibres (myelinated) for fast, acute pain and type C fibres (unmyelinated) for slow, throbbing/dull pain
- In the dorsal horn, the primary sensory neuron will synapse with a second neuron of the spinothalamic tract
- This second order neuron immediately decussates and passes up the spinothalamic tract to the thalamus
- In the thalamus, second order neurons synapse with third order neurons leading to the sensory cortex to register pain and mediate emotional components
Briefly describe the physiological pathway in the brain thought to be involved in nicotine addiction
- Nearly all dependence-producing drugs activate the mesolimbic and/or mesocortical dopaminergic pathways
- Nicotine, via attachment to nicotinic receptors, enhances the synthesis and release of dopamine from dopamine-containing neurons in the ventral tegmental area (VTA) of the hypothalamic region
Describe the physiology behind the mechanism of action of the oral contraceptive pill
- Synthetic oestrogens inhibit FSH release by negative feedback, suppressing follicular development
- Synthetic progesterone like compounds (progestins) block the oestrogen-mediated positive feedback surge in LH release, preventing ovulation, also changes the properties of cervical mucous so that it is hostile to sperm
- Endometrial layer development is less and not favourable for implantation
The sleep-wake cycle is an example of a circadian rhythm, describe the role of the Suprachiasmatic Nucleus (SCN) and the Pineal gland in the sleep-wake cycle
- The SCN becomes activated by changes in light levels detected via the optic chiasm
- In turn, the SCN sends a signal to the pineal gland
- Once activated, the pineal gland produces melatonin (sleep hormone) which reduces arousal in the brain and leads to sleep
Describe one other type of biorhythm and provide an example
- Infradian rhythms: where each cycle happens less frequently than every 24 hours (eg. Menstrual cycle)
- Ultradian rhythms: where each cycle happens more than once in 24 hours (eg. Hormone release, heart rate, bowel activity)
Describe how calcium is removed from the muscle cell to start muscle relaxation
- Calcium needs to be removed from sarcoplasm (cytoplasm of striated muscle cells)
- Sarco Endoplasmic Reticulum Calcium ATPase (SERCA) pumps two calcium ions out of sarcoplasmic reticulum via active transport
- Plasma Membrane Associated Calcium ATPase (PMACA) actively transports calcium ions across sarcolemma membrane into extracellular space
- Calcium is also removed via Na/Ca pump by facilitated diffusion across the sarcolemma membrane into extracellular space
what are long muscle fibers good for and what are short muscle fibers good for? (in terms of type of movement)
- long fibers good for rapid movement
- short fibers good for large forces
what are the 3 types of muscle fiber, what colour do they stain with myosin ATPase, and what are they used for?
- SLOW TWITCH (type 1): oxidative, stain red, prolonged endurance activity
- FAST TWITCH (type 2a): stain red, either endurance or rapid force, quickly fatigue
- FAST TWICTH (type 2b): stain white, rapid force production, quickly fatigue
what are the 2 main types of muscle contraction?
ISOMETRIC: contraction against resistance where length of muscle remains the same
ISOTONIC: contraction against resistance where length of muscle changes
- concentric: in direction of contraction
- eccentric: opposite to direction of contraction
what effect does the muscle fiber cross-sectional area have on maximal force generated?
- the larger the fiber CSA, the larger the force generated
