Test 2 Human Biology Flashcards
Stages of digestion?
Ingestion: taking in food- put in mouth and chewed. swallowing takes it down the oesophagus and into stomach. Food is propelled through alimentary canal by peristalsis (rhythmic contractions of gut wall). Mechanical breakdown: breaking up food into smaller pieces- chewing or churning action of stomach. Digestion: chemical breakdown of complex food molecules (carbohydrates, proteins, fats) into simpler ones. Mainly in small intestine, duodenum, but is started in stomach. Absorption: the passage into bloodstream of simple food molecules such as peptides, sugars, fatty acids, vitamins, minerals, water. takes place mainly in the ileum of the small intestine Egestion: the elimination of undigested food materials from the body.
Stages of digestion?
Ingestion: taking in food- put in mouth and chewed. swallowing takes it down the oesophagus and into stomach. Food is propelled through alimentary canal by peristalsis (rhythmic contractions of gut wall). Mechanical breakdown: breaking up food into smaller pieces- chewing or churning action of stomach. Digestion: chemical breakdown of complex food molecules (carbohydrates, proteins, fats) into simpler ones. Mainly in small intestine but is started in stomach. Absorption: the passage into bloodstream of simple food molecules such as peptides, sugars, fatty acids, vitamins, minerals, water. takes place mainly in the ileum of the small intestine. Egestion: the elimination of undigested food materials from the body.
Humans cannot make our own food, so we are…
Heterotrophs
DS role of mouth?
Ingestion: food enters DS through mouth and is crushed&ground by teeth. Muscular tongue moves food in mouth
DS role of salivary glands?
Already during ingestion, saliva lubricates food and contains enzymes that kickstart digestion
Components of saliva?
Digestive enzymes: salivary amylase -> starches Mineral salts Water Mucin- glycoprotein lubricant Lysozyme- bactericide
DS role of oesophagus?
Thick-walled muscular tube that connects pharynx (throat) with stomach
Throat fancy word?
Pharynx
DS function of liver?
Processes absorbed nutrients, detoxifies harmful substances and produces bile
Bile?
Green and bitter substance that helps digestion in small intestine. Produced by gall bladder in liver. Contains water, bile salts, bile pigments, cholesterol. Bile pigments break down old red blood cells, hence the green colour. Bile salts are organic molecules with a permanent charge. As a salt it is hydrophilic. They surround globular lipids and provide space for lipase enzyme to work in the spaces. Functions of bile salt: 1. Solubilise 2. Neutralise chyme from stomach 3. Stimulate peristalsis 4. Allow excretion of cholesterol, lipids, bile pigments
DS function of stomach?
Churns, digests, and stores food.
What happens in the stomach?
Low pH environment ~2 - most bacteria cannot survive Activates some digestive enzymes: PEPSIN! Produced when pepsinogen is secreted by stomach lining and is activated by HCl in stomach. Pepsin is an endopeptidase enzyme- breaks peptide bonds into proteins, making smaller chains. Then an exopeptidase enzyme breaks p-bonds on terminal ends, leaving monomers that can be absorbed. Lipase is a stomach enzyme that breaks down fats into glycerol and fatty acids. Rennin is a milk digestion enzyme. Its inactive form is prorenin and is also activates due to acid (H+) environment, causes unfolding in protein (permanent structural change). The soluble proteins in milk are caseinogena
control of digestion?
we do not eat food continuously, it is important that digestive enzymes are produced only after we have eaten. otherwise it’d be a potential danger that you’d digest yourself. 1. nervous phase- sight, smell, taste of food initiates a nerve reflex in which impulses from the brain trigger gastric glands to release their secretions 2. gastric phase (hormonal)- food in stomach stimulates the lining to secrete the hormone gastrin. it increases gastric juice secretion through direct action on gastric glands. 3. intestinal phase (hormonal)- the duodenal lining, stimulated by partially digested food, produces a second hormone, enteric gastrin. pressure sensors and chemical sensors in stomach detect stretching and the presence of chyme. the resulting nerve impulses together with the action of gastrin direct the stomach to start emptying its contents into the duodenum.
explain how the structure of the ileum relates to its function of absorbing the products of digestion.
large surface area: a lot of intestine is in contact with a lot of digested food molecules. these are absorbed by diffusion or active transport, so more membrane = more pores and carrier proteins. long intestine = more surface area. good blood supply: organ adapted for exchange of materials, so there’s a way of maintaining the diffusion gradient so that there’s always more food on one side than the other. thus ensuring that absorption is continuous and fast. as soon as food molecules enter the bloodstream, they are replaced with blood containing fewer of these molecules. thin walls: thin membrane = quick diffusion.
DS egestion in detail?
after food has been through the large intestine. the large intestine has 4 parts: caecum, colon, rectum and anus. the large int. absorbs water, is the site of manufacture of certain vitamins, forms and expels undigested food residue as faeces. saliva, gastric + pancreatic juice is reabsorbed.
alt. name of DS?
alimentary canal
types of tissue?
epithelial: thin protecting sheet e.g. skin connective: tough fibrous, keeps things in place e.g. ligaments muscular: a. skeleton- attached to skeleton that we have voluntary control over b. smooth involuntary e.g. digestive muscles c. cardic nervous: brain + spinal cord
Parts of the brain + functions?
Cerebrum: largest part of the brain. divided into 4 paired lobes- frontal, temporal, occipital, pariteal. folds in cerebrum known as grooves. deep grooves are called fissures and shallow grooves as sulci.
lognitudal fissure divides brain in half- left and right hemispheres
pituitary gland: hormone relasing-gland under the control of the hypothalamus
cerebral cortex: where thinking happens.
hypothalamus: regulation of bodily processes. coordinating system between nervous and endocrine system.
thalamus: receives sensory information and relays it to the cortex
cerebellum: takes care of things you don’t think about, controls balance and coordinates movement
matter of the brain?
grey matter: cell bodies + synapses
white matter: axons only
mentally draw a diagram of a generalised reflex arc.
components of a neurone?
from middle out:
axon: (long extension of a neurone that carries nerve impulses)
layers of lipids
—Nerves only!! (in peripheral NS)—
schwann’s cells: cells that produce myelin
myelin sheath: fatty substance that surrounds and protects some nerve fibres
node of Ranvier: gap in myelin sheath- where action potential occurs during saltatory conduction along the axon
Feedback mechanisms?
A specific mechanism known as feedback controls hormone production. involves hypothalamus, pituitary gland and the target gland. a feedback system can either promote the release of another hormone (positive feedback) or inhibit its release (negative). this involuntary mechanism maintains a balance in the body.
1. response to hormone levels
responding to levels of thyroid hormone, the hypothalamus makes TRH. this stimulates the pituitary gland to release THS. the thyroid gland is then triggered to produce its hormones.
2. Negative feedback
↑x → ↑y → ↓x
if thyroid hormone levels are too high, negative feedback alerts the hypothalamus so that it produced less TRH. A lower level of TRH results in a lower level of THS. Thyroid responds by producing less hormone. picture shows negative feedback loop
3. Positive feedback
If thyroid hormone levels fall too low, the feedback mechanism is weakened. in respone, the hypothalamus makes more THR; the pituitary gland increases secretion of TSH and the levels of thyroid hormone also rise.
