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unit 6 Flashcards

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1
Q

what is digestion?

A

the process of breaking down large food molecules into smaller molecules in order to make them soluble so they can be absorbed into the blood stream

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2
Q

what are the digestive organs?

A 
mouth
esophagus
stomach
pancreas
liver
gal bladder
small intestine
large intestine
rectum
anus
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3
Q

what does the mouth do in digestion?

A
  • mechanical digestion (chewing) & chemical digestion (amylase).
  • saliva is produced from the salivary gland. It:
  • moistens food to make a bolus for swallowing
  • contains amylase, which breakdown starch into maltose.
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4
Q

what does the esophagus do in digestion?

A

pushes down bolus to the stomach by peristalsis (mechanical)

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5
Q

what does the stomach do in digestion?

A
  • mechanical (by peristalsis) and chemical digestion (by enzymes)
  • secretes HCL which:
    1. kills bacteria and other harmful organisms preventing food poisoning
    2. provides optimum pH for pepsin (pH 1.5 - 2)
  • secretes mucus which protects the surface of the stomach from HCl
  • secretes pepsin which starts the digestion of proteins into polypeptides and amino acids. These can then be absorbed by the villi in the small intestine.
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6
Q

what are the parts of the small intestine & what do they do?

A
  1. duodenum (top part) - where chyme enters (mechanical)
  2. jejunum (middle part) - helps to further digest chyme from the stomach
  3. ileum (bottom part) - absorbs products of digestion (monomers), vitamins & minerals into the bloodstream via the villi
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7
Q

what does the small intestine do in digestion?

A
  • receives bile from the liver
  • more alkali for enzymes to work better
  • where the majority of digestion occurs
  • breaks down fats, proteins and carbs
  • internal wall secretes enzymes + gets enzymes from the pancreas
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8
Q

what does the large intestine do in digestion?

A
  • moves undigested material along to the rectum to be excreted. .
  • temporary storage of feces, and then excretion through the anus.
  • absorbs water.
  • manufactures vitamin K
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9
Q

what do the liver & gal bladder do in digestion?

A

bile is secreted by the liver and stored by the gall bladder. It helps in the digestion of lipids as it emulsifies fats.

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10
Q

what does the pancreas do in digestion?

A
  • secretes enzymes into the lumen of the small intestine.

- examples of pancreatic enzymes: Pancreatic lipase, pancreatic amylase and endopeptidases (e.g Trypsin).

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11
Q

what is the role of enzymes in digestion?

A
  • break down large, insoluble food molecules into small, soluble molecules (by hydrolysis) so that these can eventually be absorbed.
  • lower the activation energy for the reaction and therefore speed it up.
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12
Q

examples of digestive enzymes - amylase

A
  1. salivary amylase - secreted by salivary glands - breaks down starch (poly) into maltose (di) - pH 7
  2. pancreatic amylase - secreted by pancreas - breaks down starch into maltose - pH 7
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13
Q

examples of digestive enzymes - protease

A
  1. pepsin - found in stomach lining - proteins (polypeptide) into AA - pH 1.5 / 2
  2. trypsin - secreted by pancreas - protein into AA - pH 7.7/8
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14
Q

examples of digestive enzymes - lipase

A

pancreatic lipase - secreted by pancreas - triglycerides into glycerol & fatty acids - pH 7

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15
Q

what is the importance of digestion?

A

macromolecules (large and insoluble food molecules) need to be broken into monomers (smaller and soluble molecules) to be absorbed by the villi in the SI through diffusion, facilitated diffusion or active transport.

food needs to be broken down and reassembled: the food we eat is made up of many compounds made by other organisms which are not all suitable for human tissues and therefore these have to be broken down and reassembled so that our bodies can use them.

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16
Q

what is bile?

A
  • an alkaline fluid that is discharged into the duodenum to neutralize the acidity of the food coming from the stomach so lipase can work at its optimal pH
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17
Q

what is peristalsis?

A
  • peristalsis moves food through the alimentary canal
  • contraction of longitudinal muscle expand the lumen in front of the food giving it space to move into
  • contraction of the circular muscles behind the food to propel it forward
  • in the SI peristalsis also mixes food with enzymes and forces products of digestion into contact with the wall of the intestine
  • so in the intestines the food is moved very slowly to allow time for digestion
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18
Q

what is absorption in digestion?

A

the taking in of digested food substances, minerals and vitamins from the lumen of the SI into the blood

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19
Q

what is assimilation in digestion?

A

the movement of digested food molecules into the cells of the body where they are used.

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20
Q

simple diffusion in digestion

A
  • lipids
  • non-polar so can pass freely through the hydrophobic core of the plasma membrane into the epithelial cells
  • down concentration gradient
  • passive
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21
Q

facilitated diffusion in digestion

A
  • fructose & vitamins
  • are hydrophilic & polar = cannot freely pass through the plasma membrane
  • use channel proteins to enter epithelial cells
  • down concentration gradient
  • passive
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22
Q

active transport in digestion

A
  • glucose, AA & mineral ions
  • is needed when the conc is lower in the lumen of the SI
  • against concentration gradient
  • requires ATP synthesized by mitochondria of the epithelial cells
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23
Q

what is the lumen?

A

the cavity where digested food passes through & from where nutrients are absorbed

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24
Q

what is the general structure of the intestines?

A

(from outside of the tube to the inside)

  • serosa (outermost layer)
  • longitudinal muscles (peristalsis)
  • circular muscles (peristalsis)
  • submucosa (contains large veins & arteries)
  • mucosa (innermost layer where villi form)
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25
Q

describe the structure of a villus

A
  • finger like projection
  • inside is veins, lacteal & blood capillaries
  • has epithelial cells on the surface
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26
Q

what is the function of the villi?

A
  • increase the SA of epithelium

- absorb monomers formed by digestion as well as mineral ions and vitamins

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27
Q

explain the digestion & absorption of starch

A

digestion:
- starch consists of amylose (1-4) and amylopectin (1-4 & 1-6)
- amylase breaks down amylose into maltose
- maltase digests maltose into G monomers
- dextrinase breaks down amylopectin 1-6 bonds bcuz amylase cant - makes G monomers
absorption:
- G is co-transported (form of active transport = needs ATP) with sodium ions into the epithelial cells (of the villus)
- G moves by facilitated diffusion into the lumen of the villus
- G diffuses a short distance into the adjacent capillaries where it dissolves into the blood plasma
- blood in the capillaries moves to venules then to the hepatic portal vein which transports the glucose to the liver
- the liver absorbs excess glucose which it converts to glycogen for storage

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28
Q

dialysis tubing for modelling digestion

A
  • dialysis is the separation of smaller molecules from larger molecules in a solution by selective diffusion through a partially permeable membrane
  • visking tubing is partially permeable cellulose tubing that contains microscopic pores - allows water, small molecules & ions to pass but no large molecules
  • used to model SI - tube represents epithelium of SI, outside represents blood
  • glucose molecules are small enough to diffuse through the pores in the tube - down conc gradient
  • starch molecules are too large, so they stay inside tube
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29
Q

what is the blood composed of?

A

red blood cells, white blood cells, platelets, plasma

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30
Q

what is transported by the blood?

A

nutrients, oxygen, carbon dioxide, hormones, antibodies, urea and heat

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31
Q

what did William Harvey discover?

A
  • proved that the venous blood flowed to the heart and that the valves in the veins maintained the one-way flow.
    1. ligatured an arm to make obvious the veins and their valves
    2. pressed blood away from the heart and showed that the vein would remain empty because blocked by the valve.
    3. tried to force blood in a vein down the forearm but to no avail.
    4. when he tried to push it up the arm, it moved easily.
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32
Q

what is vasoconstriction?

A
  • the narrowing of blood vessels - reduces the volume or space inside affected blood vessels = blood flow is also reduced
  • at the same time, the resistance or force of blood flow is raised = higher blood pressure
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33
Q

what is vasolidation?

A
  • the widening of blood vessels - enhances blood flow to areas of the body that are lacking oxygen and/or nutrients
  • causes a decrease in systemic vascular resistance (SVR) and an increase in blood flow = reduction of blood pressure.
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34
Q

what are coronary arteries?

A

arteries that branch off the aorta & surround the heart, ensuring that it gets all the oxygenated blood it needs

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35
Q

what are the risk factors for CHD?

A
  • age (blood vessels become less flexible with advancing age)
  • diet (diets rich in saturated fats, salts and alcohol increases the risk)
  • smoking (nicotine causes vasoconstriction, raising blood pressure)
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36
Q

what is atherosclerosis?

A

the hardening and narrowing of the arteries due to the deposition of cholesterol

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37
Q

what causes atherosclerosis?

A
  • fatty deposits and cholesterol develop in the coronary arteries.
  • this causes the arteries to become narrow.
  • the restricted blood flow increase pressure in the artery, causing the damage of the artery wall.
  • cholesterol, plaque and fibrous tissue build up in the damaged region.
  • if plaque ruptures, blood clotting is triggered, forming a thrombus that restricts blood flow.
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38
Q

what is the consequence of atherosclerosis?

A
  • thrombosis in the coronary artery may block blood flow to heart muscle
  • if a coronary artery is blocked, a section of the heart doesn’t get enough nutrients and oxygen causing heart attack
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39
Q

what do both sides of the heart do?

A
  • left = pumps oxygenated blood around the body

- right = pumps deoxygenated blood to the lungs

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40
Q

explain the cardiac cycle

A
  1. deoxy blood flows into right atrium from vena cava
  2. atrial systole blood is forced into the right ventricle
  3. atrial diastole - slight delay - ventricular systole
  4. increase in pressure in the ventricle - tricuspid valves shut and semi lunar valves open
  5. blood flows into pulmonary artery
  6. ventricular diastole - lower pressure in ventricle - higher pressure in p artery = semi lunar valves shut
  7. blood travels to lungs becomes oxygenated - travels back to left atrium via pulmonary vein
    (process repeats on left side)
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41
Q

how is the heart beat initiated/controlled?

A
  • the heart muscle can contract by itself. This is called myogenic muscle contraction.
  • the heart beat is initiated by a group of specialized muscle cells in the right atrium called the sinoatrial node (SA node).
    · The SA node acts as a pacemaker - sends out an electrical signal that stimulates contraction of the atria.
  • another region in the right atrium called the atrioventricular node( AV node )receives the signal from the SA node, and then sends out another signal.
  • the 2nd signal causes the contraction of the ventricles.
  • this explains why both atria, and then both ventricles contract together.
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42
Q

how is heart rate controlled?

A
  • can be increased or decreased by impulses brought to the heart through two nerves from the medulla of the brain.
    1. cranial nerve: carries signals from the medulla to the pacemaker /\ HR.
    2. vagus nerve: carries signals from the medulla to the pacemaker \/ HR.
43
Q

what is an example of heart rate control?

A

during exercise - the heart rate needs to /\ due to the /\ demand for O for cell respiration. the body also needs to get rid of the /\ level of CO2 that accumulate in the bloodstream.

  1. when exercise = CO2 level /\
  2. the medulla senses the /\ in CO2
  3. the medulla sends a signal through the cranial nerve to the SA node to /\ heart rate to an appropriate level.
  4. when exercise is finished, the CO2 level in the blood \/.
  5. the medulla sends another signal through the vagus nerve to the SA node to \/ heart rate.
44
Q

what is a pathogen?

A

an organism or virus that causes a disease

e.g. bacteria, virus, protista & fungi

45
Q

what are the body’s lines of defence?

A 
first = surface barriers - skin & mucous membrane
second = non-specific immune response by phagocytes
third = specific immune response by lymphocytes
46
Q

primary defences against pathogens - skin

A
  • forms a physical barrier that prevents pathogens from entering the body as the outer layer is very tough.
  • contains sebaceous glands which secret lactic acid and fatty acids which creates an acidic environment on the surface of the skin preventing the growth of pathogens.
47
Q

primary defences against pathogens - mucous membranes

A
  • soft and moist areas of skin found in the trachea, nose, vagina and urethra - are not strong enough to create a physical barrier but they do have mucus which:
  • contain lysozyme enzymes that break down the pathogens.
  • can be sticky such as in the trachea, and trap the pathogens which are then expelled up the trachea and out of the body by muscles within the trachea.
48
Q

how do blood clots form?

A
  1. damaged cells and platelets release clotting factors into the plasma at a wound site.
  2. clotting factors cause the formation of thrombin; from its inactive form prothrombin.
  3. thrombin catalyzes the conversion of soluble fibrinogen into the insoluble fibrous protein fibrin.
  4. fibrin captures red blood cells and forms a solid ‘plug’ for the wound. This plug is called a clot.
49
Q

what is a cause of blood clotting in the coronary arteries?

A

atherosclerosis

50
Q

explain the process of phagocytosis (non-specific immune response)

A
  1. immune cells are attracted to pathogen by chemical products of the microorganism
  2. phagocytes attach by surface receptors to the pathogen and surround it
  3. phagocyte ingests the pathogen (phagocytosis), and the particle is enclosed in a vesicle called a phagosome.
  4. the phagosome transports the particle into the cell.
  5. lysosome fuses with the phagosome and the pathogen is digested.
  6. lysosomes are vesicles that contain hydrolytic enzymes that break down molecules.
  7. cellular waste, such as broken down molecules that the cell cannot reuse, is discharged from the cell by the process of exocytosis.
51
Q

what is an antigen?

A

a foreign substance, often found on a cell or virus surface, which stimulate the production of antibodies.

52
Q

what is an antibody?

A
  • proteins that defend the body against pathogens by binding to antigens on the surface of these pathogens and stimulating their destruction.
  • specific to certain antigens.
  • produced by B-cells + form a Y shape
53
Q

explain specific immunity

A
  • antibodies are found on the surface of the lymphocytes with the antigen-binding site projecting outwards.
  • each lymphocyte (B cell) makes only one specific antibody.
  • pathogens have antigens on their surface.
  • each antibody recognizes specific antigen.
  • antibodies attach to an antigen and attract cells that will engulf and destroy the pathogen.
  • the lymphocyte becomes active and starts to make clones of itself by dividing by mitosis.
  • lymphocytes then divide to form clones of plasma cells and memory cells.
  • plasma cells produce large quantities of antibodies specific to the antigen.
  • memory cells provide long-term immunity as they remain circulating in the bloodstream waiting for a secondary infection to produce more antibodies and cause a faster response.
54
Q

how was penicillin discovered?

A

Alexander Fleming saw areas clear of microorganism growth surrounding the mold gathering on the unwashed petri dishes in his lab. He was able to extract the prototype for the first antibiotic.

55
Q

explain Florey and Chain’s experiment

A

infected mice with pathogenic bacteria - half were then given penicillin injections and the other half were not given anything. The mice with no further treatment all died, and the ones with penicillin all survived. concluded penicillin has antibiotic properties

56
Q

what are antibiotics?

A

drugs that kill or prevent the growth of bacteria without killing healthy body cells

57
Q

how do antibiotics work?

A

block metabolic process that occur in the prokaryotic cells

58
Q

why are antibiotics not effective against viruses?

A
  • antibiotics are designed to disrupt structures or metabollic pathways in bacteria or fungi (e.g. protein synthesis)
  • viruses lack a metabolism and cannot therefore be treated with antibiotics.
  • they rely on a host cell (a human cell) to reproduce and thus it is impossible to harm the virus without harming the human cells.
59
Q

what is HIV/AIDS?

A 
HIV = Human Immunodeficiency Virus
AIDs = Acquired Immunodeficiency Syndrome

HIV is the pathogen, AIDs is the infectious disease

60
Q

what causes AIDs?

A
  • HIV causes AIDS.
  • HIV destroys the T lymphocyte vital for antibody production.
  • overtime there are fewer active lymphocytes = \/ in the number of antibodies produced.
  • the immune system is weakened and the body becomes very vulnerable to pathogens.
  • pathogens that would normally be easily controlled by the body in healthy individuals can cause serious consequences and eventually lead to death for patients affected by HIV.
61
Q

how is HIV transmitted?

A

through body fluids from an infected person to an uninfected one

62
Q

what does ventilation do?

A

maintains concentration gradients of oxygen and carbon dioxide between air in alveoli and blood flowing in adjacent capillaries.

63
Q

why do we need ventilation?

A
  • the body needs O to make ATP via cell respiration

- O needs to diffuse from alveoli into blood, CO2 needs to diffuse from blood into alveoli

64
Q

what is ventilation?

A
  • the process of bringing fresh air into the alveoli and removing the stale air in two stages: inspiration and expiration
  • controlled by movement of the diaphragm & ribcage
  • maintains the concentration gradient of CO2 and O between the alveoli and the blood in the capillaries
65
Q

what is gas exchange?

A
  • the process of swapping one gas for another
  • occurs in the alveoli of the lungs
  • O diffuses into the capillaries from the air in the alveoli and CO2 diffuses out of the capillaries and into the air in the alveoli
66
Q

what is cell respiration?

A
  • the controlled release of energy from organic compounds in cells to produce ATP
  • occurs at the mitochondria
67
Q

adaptations of alveoli

A
  1. huge numbers of alveoli = increased surface area = more gas exchange
  2. they are very thin (only 1 cell thick) = short diffusion pathway
  3. moist lining inside each alveoli sack = allows gasses to dissolve then diffuse
68
Q

what are the 2 types of cells that make up the alveoli wall?

A

type I pneumocytes

function: carry out gas exchange
adaptations: extremely thin (flattened) & single layer
advantage: shortens the distance for diffusion - allow rapid diffusion - allow rapid gas exchange.

type II pneumocytes

function: secrete a solution containing surfactant that creates a moist surface inside the alveoli
advantage: prevents the sides of the alveolus adhering to each other by reducing surface tension.

69
Q

describe the structure of the ventilation system

A
  • ventilation occurs within the lungs
  • trachea divides to form 2 bronchi, which divide to form bronchioles
  • alveoli are tiny air sacs at the end of the bronchioles
  • alveoli are very small but there are many of them = large total surface area
  • wall of alveoli is very thin - single layer of cells
  • surrounded by a network of capillaries
70
Q

inspiration and expiration

A

inspiration = breathing in

  1. diaphragm contracts = becomes flat
  2. external intercostal muscles also contract = ribcage moves up & out
  3. internal intercostal muscles relax (antagonistic muscle action)
  4. vol of lungs /\ = pressure inside lungs is less than pressure of the atmosphere
  5. air flows passively into the lungs

expiration = breathing out
OPPOSITE

71
Q

what causes lung cancer?

A

occurs when abnormal cells grow out of control in the lung - can invade nearby tissue and form tumours

smoking

  • no 1 cause
  • there is an extremely high correlation with the number of cigarettes smoked in a day and the incidence of lung cancer
  • cigarettes contain a high number of carcinogens
72
Q

what does ‘antagonistic muscle pair’ mean?

A

when 2 muscles work together to perform opposite tasks - when one contracts the other relaxes

73
Q

what is emphysema?

A
  • a condition in which the air sacs of the lungs are damaged and enlarged (bcuz their walls break down or air sacs are destroyed)
  • causes fatigue - damaged alveoli = less gas exchange bcuz their is less SA = less O carried in blood cells = less respiration = less energy produces = tired
74
Q

what are 4 symptoms of lung cancer?

A
  1. a long-standing cough that gets worse
  2. an ache or pain when breathing or coughing
  3. persistent breathlessness
  4. persistent tiredness or lack of energy
75
Q

what are the 2 parts of the nervous system?

A

central nervous system (CNS)
- consisting of the brain and spinal cord

peripheral nervous system (PNS)
- connects all parts of the body to the CNS, consisting of motor and sensory nerves.

76
Q

what are the 3 types of neurons?

A
  1. sensory - carry nerve impulses from receptors (sensory cells) to the CNS.
  2. motor - carry nerve impulses from the CNS to effectors (muscle and gland cells).
  3. relay - carry nerve impulses within the CNS from one neuron to another.
77
Q

what is the impulse pathway?

A

stimuli - receptor - sensory nerve - relay nerve - motor neuron - effector - response

78
Q

what is resting potential?

A

the normal, resting state of an axon
p.d across the axon is - 70 mV
during this state the membrane is polarized

79
Q

what is action potential?

A

a nerve impulse
occurs when the p.d across an axon is temporarily reversed - changes to +35 mV
membrane is depolarized

80
Q

what is the refractory period?

A

the time needed for the concentration gradients of Na+ and K+ ions to be restored by active transport.

81
Q

what are synapses?

A

junctions between the pre-synaptic and post-synaptic neurons

82
Q

what are the stages in synaptic transmission?

A
  1. when an action potential reaches the axon terminal, it triggers the opening of voltage-gated Ca channels
  2. Ca ions diffuse into the cell and promote the fusion of vesicles (containing NTs) with the cell membrane
  3. the NTs are released from the axon terminal by exocytosis and cross the synaptic cleft
  4. NTs bind to specific receptors on the post-synaptic membrane and open ligand-gated ion channels
  5. the opening of ion channels generates an electrical impulse in the post-synaptic neuron, propagating the pre-synaptic signal
  6. the NTs released into the synapse are either recycled (by reuptake pumps) or degraded (by enzymes)
83
Q

explain the secretion and reabsorption of acetylcholine (ACH)

A
  • ACH is a neurotransmitter - is largely used at the neuromuscular junction, meaning it is released by motor neurons and binds to receptors on muscles.
    1. ACH is created in the presynaptic terminal by combining a water-soluble nutrient called choline with an acetyl group
    2. ACH is secreted by the presynaptic membrane of a neuron
    3. the NT diffuses across the synapse and binds to a receptor on the post synaptic membrane (causing an action potential if a threshold is reached)
    4. once it is released from the receptor, an enzyme called acetylcholinesterase breaks it down into choline and acetate
    5. choline is reabsorbed back into the pre-synaptic neuron where it is combined with another acetyl group to form another ACH NT
84
Q

what is the myelin sheath?

A

a type of tissue formed by specialized cells called schwann cells
speeds up action potential / impuse

85
Q

how does myelination increase the speed of an action poteintial?

A
  • as myelin acts as an insulator, myelinated axons only allow AP to occur at the unmyelinated nodes of Ranvier
  • this forces the AP to jump from node to node (saltatory conduction)
  • this is much quicker than the step-by-step conduction that occurs in a non-myelinated neurone
86
Q

what is the endocrine system?

A
  • consists of glands that release hormones that are transported in the blood.
  • the hormones travel in blood to target tissue (effector) that brings about a response.
  • the response modifies the internal environment and this becomes feedback stimuli.
87
Q

explain the response to high blood glucose levels

A
  • β cells in the pancreatic islets produce insulin.
  • insulin stimulates muscle cells and the liver cells to take up glucose from the blood and convert it into glycogen.
  • other types of cells are stimulated to take up glucose and use it for cell respiration instead of fat.
  • all of these processes lower the levels of glucose in the blood.
88
Q

explain the response to low blood glucose levels

A
  • α cells in the pancreatic islets produce glucagon.
  • glucagon stimulates the liver cells and muscle cells to convert glycogen back into glucose and release this glucose into the blood.
  • this raises the glucose levels in the blood.
89
Q

what are the causes & treatments for type I diabetes?

A

causes:

  • onset is usually early, sometime during childhood.
  • β cells do not produce enough insulin due to an autoimmune disease.

treatment:

  • insulin injections are needed to control glucose levels.
  • diet by itself cannot be used to control the condition.
90
Q

what are the causes & treatments for type II diabetes?

A

causes:

  • onset is usually late, sometime after childhood.
  • target cells become insensitive to insulin.
  • pancreas is producing insulin but the insulin receptors on the liver and muscle cells lose their ability to respond to insulin.
  • obesity/ genetic factor.

treatment:

  • insulin injections are not usually needed.
  • low carb diet can control the condition.
  • high fiber diet/ exercise
91
Q

what is thyroxin?

A
  1. a hormone that is secreted:
    - by the thyroid gland under the influence of thyroxin stimulating hormone
    - in two forms: T3 and T4
  2. it contains iodine = prolonged deficiency to iodine in the diet prevents the production of thyroxin
  3. regulates the metabolic rate and help control body temperature:
    - /\ metabolic rate
    - /\ body temp
  4. thyroxin levels are maintained within narrow limits by negative feedback.
  5. if there is an excessive amount of thyroxin in the body, hyperthyroidism can occur.
  6. if there is an insufficient amount of thyroxin in the body, hypothyroidism can occur.
92
Q

what is leptin?

A

hormone secreted by cells in adipose tissue

  • acts on the hypothalamus of the brain to inhibit appetite.
  • the conc of leptin in the blood is controlled by: food intake and the amount of adipose tissue in the body
  • if the amount of adipose tissue in an individual /\, then their conc of leptin also /\, leading to long term suppression of appetite and reduced food intake
  • in obese individuals a \/ sensitivity to leptin can occur, resulting in an inability to recognize when they are full
93
Q

what is melatonin?

A

a hormone secreted by the pineal gland

  • the secretion of melatonin is controlled by cells in the hypothalamus.
  • light exposure to the retina is relayed to the suprachiasmatic nucleus (SCN) of the hypothalamus. - - - these fibers from the hypothalamus relay a message to the nerve ganglia of the spinal cord which is relayed back to the pineal gland to release melatonin.
  • melatonin helps control your sleep and wake cycles (circadian rhythms).
94
Q

What does the SRY gene do?

A
  • gonads can become either ovaries or testes.
  • if there is no Y chromosome present, the gonads become ovaries, meaning the fetus is female.
  • if there is a Y chromosome, the SRY gene is present.
  • SRY encodes for a protein called testis determining factor (TDF), a DNA binding protein which acts as a transcription factor which causes the growth of testes
95
Q

what do testosterone and estrogen/progesterone do?

A

testosterone causes…

  1. pre-natal development of male genitalia
  2. sperm production
  3. development of male secondary sexual characteristics during puberty.

estrogen and progesterone…

  1. cause pre-natal development of female reproductive organs
  2. development of female secondary sexual characteristics during puberty.
  3. both have a role in the menstrual cycle.
96
Q

explain the sperm’s journey

A
  1. spermatogenesis (production) in the testis
  2. maturation in the epididymis
  3. carried along vas deferens
  4. fructose for energy & protective mucus are picked up at the seminal vesicle
  5. prostate adds fluids to neutralize acid in the vagina
  6. ejaculation through penis via the urethra
97
Q

what does the follicle stimulation hormone do?

A
  • produced in anterior pituitary gland
  1. stimulates the development of follicles.
  2. develops the oocyte in the follicle.
  3. stimulates the secretion of estrogen from the follicle.
98
Q

what does the luteinizing hormone do?

A
  • produced in anterior pituitary gland
  1. causes ovulation (oocyte release).
  2. stimulates the development of the corpus luteum (which secretes progesterone)
  3. stimulates the follicle cells to secrete less estrogen
99
Q

what does estrogen do?

A

produced in the ovaries

  1. promotes follicular development;
  2. governs development of secondary sexual characteristics;
  3. stimulates uterine and breast growth
  4. stimulates the development of the endometrium
100
Q

what does progesterone do?

A
  • produced in ovaries
  1. maintains the lining of the endometrium to prepare it for implementation.
  2. inhibits the secretion of FSH and LH (negative feedback on FSH and LH)
101
Q

what are the 3 basic components of a neuron?

A
  1. dendrites – short-branched fibres that convert chemical info from other neurons or receptor cells into electrical signals
  2. axon – an elongated fibre that transmits electrical signals to terminal regions for communication with other neurons or effectors
  3. soma – a cell body containing the nucleus and organelles
102
Q

adaptations of arteries

A
  • narrow lumen to maintain high blood pressure
  • have a thick wall containing an outer layer of collagen to prevent the artery from rupturing under the high pressure
  • arterial wall also contains an inner layer of muscle and elastic fibres to help maintain pulse flow
103
Q

adaptations of capillaries

A
  • have a very small diameter which allows the passage of only a single red blood cell at a time (optimal exchange)
  • the capillary wall is made of a single layer of cells to minimise the diffusion distance for permeable materials
  • they are surrounded by a basement membrane which is permeable to necessary materials
104
Q

adaptations of veins

A
  • have a very wide lumen to maximise blood flow for more effective return
  • have a thin wall containing less muscle and elastic fibres as blood is flowing at a very low pressure
  • have valves to prevent backflow and stop the blood from pooling at the lowest extremities

IB biology sl (6 decks)

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