Human Physiology Flashcards
1
Q
What is homeostasis?
A
Homeostasis - maintaining relatively constant internal environment through dynamic change
- in animals, homeostasis mainly relies on negative feeedback [Helps to return a variable to a normal range (temp, blood glucose levels) ]
2
Q
How does feedback help the nervous system regulate homeostasis?
A
- NS plays central role in processing/responding sensory info from feedback system
1. Sensory Input: - NS uses sensory systems to detect changes in environment (int/ext) -> receptors convert stimuli to electrical signals transmitted to brain + spinal cord
1. Feedback Loops - Negative: oposes initial change - brings system back to stable state
ex. Blood sugar levels are too high, pancreas releases insulin to lower - PositiveL amplifies initial change
ex. During childbirth uterine contractions stimulate release of oxytocin (further intensifies)
3
Q
What are the organs of the CNS (central nervous system)?
A
- Brain
- Spinal cord
Located in dorsal body cavity (lies close to spine in posterior portion of body - containing spinal column, central nervous system (brain and spinal cord) and meninges - cerebrospinal fluid provides protection for brain + spinal cord within
4
Q
What are characteristics of the nervous system?
A
- Hard-wired
- Fast-acting (milliseconds)
- Electrical/chemical signaling
- Local cellular response
- Rapid response by target cell
5
Q
What is a sensory nerve receptor?
A
- A nerve ending that transduce stimulus energy + sends signals to the CNS
- buliding percepts require complex processing of sensory info
- Allows brain to receive information from various systems + body parts (internal/external)
6
Q
What is the path of sensory reception and response due to multisensory perception?
A
- Multiple receptors detect stimuli
- Stimulus energy converted to electrical energy at cell membrane
- Action potentials fire in nerve afferents
- Information detected, processed and integrated by multiple regions of CNS
- Involuntary response OR modulation of behaviour
7
Q
What are afferent neurons compared to efferent neurons in the PNS?
A
- Afferent neurons (“sensory neurons”) carry info from sensory receptors of the skin (& other organs) TO the CNS
- cell bodies outside CNS (dorsal root ganglia)
- Efferent neurons carry motor informaton AWAY from CNS -> muscles + glands of body
- cell bodies within the CNS
8
Q
How do PNS and CNS interact?
A
- Afferent neurons provide input to CNS -> recieves info from body through afferent neurons to asses state of body/environ
- Efferent neurons receive output from CNS - sends motor commands to body through efferent neurons
CRUCIAL FOR:
- Reflexes - rapid, involuntary actions
- Voluntary movemements:
- Homeostasis
9
Q
What is the Peripheral Nervous System?
A
- Sensory afferents of PNS send info from internal/external environment –> CNS
-Network of spinal and cranial nerves linked to brain and spinal cord - contains sensory receptors -> info sent to CNS via afferent sensory nerves
- Divided into Autonomic and Somatic systems (2 efferent components)
10
Q
What is the SNS (somatic system)?
A
- Relies on motor system
- Carries signals to skeletal muscles and mainly is voluntary
11
Q
What is the Autonomic Nervous system?
A
- Regulates smooth + cardiac muscles
-generally involuntary
-Involves internal environment activity - Divided into Sympathetic and Parasympathetic divisions
12
Q
What is the Sympathetic division?
A
“fight-or-flight” response
- regulates arousal + energy generation
- prepares body for action
- originates from thoracic and lumbar regions of spinal cord
- Example: pupil dialates, accelerates heart, inhibits stomach activity, stimulates glucose release
13
Q
What is the Parasympathetic division?
A
- “rest-and-digest”
- promotes relaxation + help body conserve energy
- originate from brain and sacral regions of spinal cord
-Examples: constricts pupil of eye, stimulates salivary gland secretion, stimulates activity of pancreas, slow heart rate
14
Q
What are sympathetic ganglia?
A
- Clusters of nerve cell bodies within sympathetic nervous system
- act as relay stations - connect CNS to rest of body to regulate functions
- located along sympathetic chain
15
Q
What is the neuromuscular junction?
A
- final common pathway by which regions of CNS exert control over skeletal muscle through motor units
- areas like spinal cord, motor regions of cortex, basal nuclei, cerebellum, brain stem
16
Q
What is ANS signaling?
A
- Describes how ANS communicates with target organs and tissues (for functions like heart rate + digestion)
- ANS uses neurotransmitters to transmit signals
- efferent pathways
17
Q
What is the efferent 2 neuron pathway in Sympathetic and Parasympathetic divisons?
A
- consists of preganglionic fibers and postganglionic fibers
- Preganglionic fibers originate in the CNS + axons excit the CNS -> synapse in autonomic ganglia + releases n.t Ach (acetylcholine)
- Postganglionic fibers - neuron cell body in autonomic ganglia -> target organs to innervate
- in SNS = usually NE released
- in PNS - release Ach
- cholinergic recpetors in tissues bind Ach
- andrenergic receptors bind Noradrenaline and adrenaline in tissues
18
Q
What is the endocrine system?
A
- Function: regulates body internal environment chemical signaling by hormones produced by endocrine glands
- hormone release helps control mood, growth, reproduction, development to compliment nervous system
- Key aspects: thyroid, pituitary gland, parathyroid gland + testes/ovaries
- reacts slowly + often long-lasting effects
19
Q
What are hormones? What are the classes of hormones?
A
- Hormones are chemical signals secreted into circulatory system - communicate regulatory messages to target cells
- 3 classes:
1. Polypeptides: water-soluble, hydrophilic, essentially “protein” hormones
2. Amines: water-soluble, amino acid derivatives
3. Steroids: non-polar, lipid-soluble
Endocrine (released in blood), Paracrine (released and act on target organs), Autocrine hormones (released and act on self)
20
Q
What are key differences between lipid-soluble and water-soluble hormones?
A
- Water-soluble:
- secreted by exocytosis
- travel freely in blood
- bind to cell-surface receptors - Lipid-soluble:
- diffuse across cell membranes
- ytravel in bloodstream bound to transport proteins
- diffuse through membrane of target cells
- binds to recpetors in cytoplasm or nucleus of target cells (inside of cell)
21
Q
Exocrine glands vs endocrine glands?
A
- Endocrine glands = ductless organs containing groups of endocrine cells (those that produce true hormones) - hormones secreted into blood
- Exocrine glands = have ducts to carry secreted substances onto body surfaces/into body cavities
22
Q
How is endocrine signaling coordinated?
A
- By Hypothalamus
- receives info from nerves through body from NS
- initiates appropriate neuroendocrine signals
- Sends hormones to pituitary gland: TRH (thyrotpin) -> stimulates thyroid-stimulating hormone; CRH (corticotropic) -> stimulates adrenocorticotropic hromone; GNRH -> leutinising hormone and follicule stimulateing hormone; GHRH -> growth hormone release; somatostatin (GHIH) -> inhibits growth hormone; dopamine -> inhibits prolactin release
23
Q
What is the pituitary gland and what is its role in the endocrine system?
A
- Located at base of hypothalamus in Sella Turcia cavity
- Moniters and regulates many bodily functions through producing + releasing several hormones
- produces growth hromone
- Hormones from pituitary influence metabolism
- Releases hromones like FSH and LH for sex development
- ADH helps regulate water + salt balance
- Prolactin stimulates milk production
- Posterior and Anterior divisions
24
Q
Compare and contrast the Anterior and Posterior pituitary divisions.
A
Anterior Pituitary:
- Makes/releases hormones under regulation of hypothalamus
-Glandular epithelial tissue
-Releases TSH (stimulates thyroid hormone secretion)
- Releass growth hormone and prolactin (breast milk production)
Posterior Pituitary:
- Neural secretory tissue
- composed of mostly unmyelinated axons - carry oxytocin (stimulates uterine contractions childbrith) and ADH (stimulates water reabsorption in collecting ducts of kidneys -concentrates urine)
25
What is the significance of the Thyroid gland?
Thyroid regulates, metabolism, growth and development
If thyroid level drops in blood -> hypothalamus secretes thyrotropin-releasing-hormone (TRH) -> causes anterior to secrete thyroid-stimulating hormone -> TSH stimulates release of thyroid hormone by thyroid gland
- disruption of hyroid hormone production/regulation results in disorders
- Thyroid hormone = only iodine-containing molecule synthesized in body; insufficient iodine - low level of thyroid hormone -> causes thyroid to enlarge -> goiter
25
What are Adrenal Glands?
- Located on top of kidneys
- Produce important hormones like cortisol, aldosterone, adrenaline
-Play crucial role in homeostasis
- help body respond to stress, manage blood pressure + blood sugar
- 2 parts: Adrenal medulla and Adrenal Cortex
26
What are the differences between the parts of the Adrenal Glands?
1. Adrenal Medulla (inner)
- secretes adrenaline and noadrenaline (fight, flight, freeze)
2. Adrenal Cortex (outer)
- secretes corticosteroids
- glucocorticoids (cortisol) - influence glucose metabolism + immune system
- mineralocorticoids (Aldosterone) - affect salt + water balance
27
How does the adrenal gland respond to stress?
- Brain percieves stressor -> hypothalamus releases CRH -> stimulates pituitary gland to release ACTH -> ACTH stimulates Adrenal cortex produce cortisol for energy boost
- Adrenal medulla releases adrenaline and norepinephrine -> hormones trigger sympathetic nervous system -> causing rapid increase in heart rate, blood pressure, breathing
- prolonged/chronic stress can disrupt HPA axis + imbalance hormone levels
28
What are sex hormones?
- Essential for development/function of reproductive organs, regulating menstrual cycle + pregnancy,; sexual development; also influence bone density, cardiovascular health and metabolism
- Gonard, testes and ovaries produce most: androgens, estrogens, progesteronee
- synthesis of sex hormones - controlled by gonadotropins
= follicule stimulating hormone + luteinizing hormone from anterior pituitary
29
What is the significance of hormones produced by the pancreas?
- Produces crucial hormones (mainly insulin and glucagon) to maintain stable blood glucose
- Islets of Langerhans - clusters of hormone-producing cells that control blood glucose regulation
- β (beta) cells = site of insulin synthesis + secretion
-α (alpha) cells = produce glucagon
30
How does insulin and glucagon work to stabilize blood glucose?
- Blood glucose FALLS (after fasting) -> glucagon secreted by alpha cells - breakdown of glycogen + release of glucose into blood
- Blood glucose RISES (after eating) -> secretion of insulin by beta cells of pancreas -> transport of glucose into body cells + storage of glucose as glycogen
31
What is the most common of all endocrine disorders?
Diabetes Mellitus
- Type 1: characterised by lack of insulin secretion; autoimmune destruction of beta cells; childhood; 10-20% of diabetics
- Type 2: characterised by normal/increased insulin secretion but reduced sensitivity of target cells; adulthood
Insulin is an anabolic hormone + promotes cellular uptake of glucose, fatty acids and amino acids
32
What are some consequences of insulin deficiency?
- Increased hepatic glucose uptake -> hyperglycemia
- Reduced glucose uptake by cells
- reduced triglyceride synthesis + increased lipolysis -> increased bloody fatty acids
- increased blood amino acids
- increased protein degradation
33
What is muscle tissue?
- Responsible for almost all types of movement
- consists of protein actin and myosin filaments - together enable contraction
- 3 types of vertebrates: Skeletal, Smooth, Cardiac
34
How does muscle activity and nervous system work together?
- Muscle activity responds to input from NS
35
How are muscle fibers composed?
- each muscle fiber is multi-nucleated
- muscle fibers subdivided into myofibrils (basic units of muscle fiber)
- myofibrils surrounded by muscle cell membrane -> form deep invaginations called transverse (T-tubules) within myofibril
- myofibril contains contractile proteins - arranged longitudinally into units (sacromeres)
- Saromeres bordered by Z lines - where actin attach
36
What are the 2 contractile filaments in myofibrils?
- Actin (and tropomyosin and troponin) is the thinner filament
- Myosin - thicker filament - made up of 2 chains that form tail and two heads -> heads lies bidning site with actin : forms a cross bridge
-Cross bridge pulling thin filament towards sacromere = power stroke
-Muscle contraction requires repeated cycling: cross-bridge cycling
37
How does skeletal muscle contract?
1. Action potential travels alone motor nerve
38
How does the cardiovascular system and the respiratory system work together?
- work to supply oxygen and remove CO2
- lungs facilitate gas exchange (PULMONARY RESPIRATION)
- CVS facilitates oxygen transport with red blood cells
- R.S removes CO2
- one cannot function without the other
39
How does pulmonary respiration work?
- Part of circulatory system that moves deoxygenated lood from the heart to lungs
- Blood that already delivered oxygen to body + picked up CO2 returns to right atrium
-Pulmonary artery carries deoxygeerated blood from right ventricle of heart -> lungs
- Artery splits into 2 main branches (for each lung)
-Carries blood toward capillaries that surround air sacs in lungs (alveoli)
- Inside alveoli, oxygen from inhalation diffuse across thin walls -> capillaries + CO2 diffuses from blood -> alveoli 4 exhalation
- Blood flows from lungs -> pulmonary veins (carry oxygenated blood) -> left atrium of heart
- Moves to left ventricle to be pumped through systemic circulation
40
How is blood composed?
I. 55% Plasma
- Water (solvent)
- Ions (blood electrolytes) : osmotic balance, pH buffering, regulation of membrane permeability
- Plasma proteins: osmotic balance, pH buffering
- Immunoglobulins (antibodies): class of proteins produced by plasma (white blood) cells, recognize + bind to foreign substances for destruction
- Apolipoproteins: lipid transport, clotting
2. Cellular elements
- Leukocytes (white blood cells): defense + immunity
-Platelets : blood clotting
- Erythrocytes (red blood cells): transport O2 and CO2
41
What substances are transported by blood?
1. Nutrients (glucose, fatty acids, vitamins)
2. Waste products of metabolism
3. Respiratory gases (O2 and CO2)
4. Hormones
42
Characteristics of the heart:
- Size of clenched fist
- Weighs 250-350g
- heart contracts + relaxes in rhythmic cycle - cardiac cycle
43
What are characteristics of cardiac cycle?
Contraction = systole
Relaxation = diastole
Cardiac cycle = 0.8 s
Heart Rate = 60/0.8 = 75 bpm
Flow = unidirection (backward flow prevented by artioventricular valve + semilunar valves)
44
Explain how the autonomic nervous system regulates cardiac function.
- ANS plays vital role in regulating involuntary functions (like in heat)
Parasympathetic: primarily acts through vagus nerve (Cranial nerve X) -> innervates the SA node (heart's natural pacemaker
- activation of pathway = release in Ach -> acts on SA node to 1) slow heart rate + 2) reduce rate of electrical conduction through heart
- usually during rest + sleep
Sympathetic:
1. Increases heart rate - release norepinephrine (stimulate adrenal medulla to release epinephrine to blood) -> increases heart rate + increases conduction speed
1. Increase contraction strength - sympathetic nerve can innervate walls of ventricles
- activation increases strength of myocardial contraction -> boosts stroke volume + improve cardiac output
- dual adjustment ensures oxygen and nutrient delivery to tissues is increased to match higher metabolic demand
45
What is sinus rhythm? How does the ANS modulate sinus rhythm?
Sinus rhythm = natural, regular heartbeat initiated by SA node - located in right atrium of heart
- "pacemaker"
- constantly adjusted by ANS based on body needs
Para: acts via vagus nerve -> innervates SA node
- releases Ach
- slows rate of firing of SA node -> causes bradycardia (slower heart rate)
- most dominant during rest and sleep (oxygen demand low)
Sympa: sends sympathetic nerve fibers -> SA node
- release norepinephrine
- increases rate of firing of SA node --> tachycardia (faster heart rate)
- stress, excitement, danger, exercise
- balance responsible for heart rate variability
46
What are hemodynamics?
How blood moves through circulation
*Fluids move from higher pressure --> lower pressure (down pressure gradient)
47
BOYLE's LAW
- at constant temp, pressure and volume = inversely related
ex. exhalation
- diaphragm relaxes --> lung volume decrease but pressure in lung increases
48
What is hemoglobin's role in oxygen export?
98.5% transported by hemoglobin - each protein can bind 4 oxygen molecules
49
What are the differences between the R.S and CVS in terms of oxygen and CO2 export?
R.S Gas Exchange at lungs
- Oxgen export (in2 body)
- inhaled oxygen moves from alveoli -> capillaries via diffusion (O2 concentration higher in alveoli) --> oxygen binds to hemoglobin in red blood cells
- CO2 Export (out body): CO2 in blood diffuses from alveoli --> exhaled + expelled from lungs
CVS Transport between Lungs and Tissues
- Oxygen transport to tissues: picks up O2 in lungs --> blood returns to left side of heart via pulmonary veins --> heart pumps out through aorta ---> oxygen delivered to body tissues + diffuses w
- CO2 transport to lungs: CO2 produced by cells during metabolism /cell respiration -> diffuses into nearby capillaries --> transported in blood in 3 forms: 1. Dissolved plasma, 2. bound to hemoglobin, 3. as bicarbonate ions (mostly) --> carried 2 right side of heart ---> pumped to lungs via pulmonary arteries ---> CO2 offloaded into alveoli + exhaled
50
What are Lymph Vessels?
- thin tubes that form network through body - collecting lymph fluid from tissues + return to blood stream
- lymph = clear, watery fluid w/ white blood cells collected from tissues
Major functions:
- tissue drainage
- return leaked plasma proteins
- absorption of digested fat
- defense (lymph nodes)
51
What causes Oedema?
- buildup of fluid in interstitial (cavities or tissues of body) via reduced plasma proteins (through loss in urine - kidney disease, reduced synthesis - liver disease, dietary sodium intake)
- fluid leakage happens when small blood vessels (capillaries leak fluid into space between cells + tissues)
- causes increased capillary permeability
- increased venous pressure (pressure in veins) can cause edema - pregnancy, airplane flight
52
What is osmoregulation?
Balances uptake + loss of water and solutes
- plasma composition regulated by kidneys
- urine = filtered plasma
53
How does renal system produce urine?
- by refining a filtrate derived from plasma
Filtration - filtering of plasma
Reabsorption - reclaiming valuable solutes
Secretion - adding nonessential solutes
Excretion - processed filtrate containing nitrogenous wastes released from body
54
Explain how the kidney is regulated to maintain homeostatic conditions.
Combo of nervous + hormonal controls manage osmoregulatory functions of mammalian kidney
- ADH (antidiuretic hormone) released from posterior pituitary bind/activate membrane receptors on collecting duct cells (from pancreas)
--> initiates signal cascade --> insertion of aquaporin proteins into membrane lining (aquaporin proteins - membrane proteins that act as water channels)
- increase in water recapture reduces urine volume
- Osmoreceptor cells in hypothalamus monitor blood osmolarity + regulate release of ADH from posterior pituitary
55
What are thr two main branches of immune system?
1. Innate Immunity
- body's first line of defense, non-specific + immediate
2. Adaptive immunity
- specific immune response that develops over time + has memory
56
What are key components of innate immunity ?
- Physical barriers (skin)
- Phagocytes (macrophages, neutrophils)
-NK cells
- inflmmation
- complement proteins
57
What are the main cell types involved in adaptive immunity?
- B cells: produce antibodies; involved in humoral immunity
- T cells: involved in cell-mediated immunity; include helper T cells + cytotoxic T cells
