Year 9 Biology

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what is the nervous system

communication system, controls all parts of your body

structure of CNS

made up of brain and spinal cord

CNS purpose

receives info from all over body, processes it and sends out msgs that tell body how to respond

structure and purpose of PNS

made up of nerves that carry out nerve impulses to & from CNS

brain purpose

control centre of body

tells diff parts of body what to do through NS nerve impulses

cerebrum

largest part of brain, made of 4 lobes

frontal lobe

higher thought (critical thinking, emotions)

occipital lobe

vision (colour, spatial awareness, movement)

parietal lobe

processes sensory info (4 other senses, body position)

cerebellum location + purpose

near rear, lower part of brain

responsible for balance, coordination + fine & gross motor movement

brainstem location

connects brain to spinal cord, located at base of brain

brainstem purpose

responsible for many involuntary processes (heartbeat, movement of stomach and intestines

midbrain location

top part of brainstem

pons location

below midbrain

medulla location

bottom-most part of brain

hypothalamus location

directly above brainstem, below thalamus + above pituitary gland

hypothalamus purpose

responsible for keeping body in a stable state: homeostasis

white matter

parts of CNS that contain neurons covered in myelin

where axons are connecting diff parts of grey matter to eachother

grey matter

parts w/ mainly cell bodies, dendrites + synaptic terminals

where the “thinking” occurs

motor neurons

carry signals from CNS to effectors

effectors

muscle cells/glands

put messages into effect

sensory neurons

carry signals from cells in sense organs to CNS

e.g. pain receptors in neck

interneurons

link sensory neurons directly to motor neurons

only make connections with other neurons

axon

carries signal away from cell body to axon terminals

dendrite location

attached to cell body

dendrite

sensitive branches that receive info as electrical signals from nerves near it

myelin sheath

fatty layer covering axon

helps speed up nerve impulse

protects impulse from “crossing wires”

cell body

contains a nucleus

axon terminal

bulb at end of axon

where electrical msg is passed across synapse to next dendrite

synapse

small gap between neurons

role of sense receptor

detects change in environment

e.g. photoreceptors detecting light

stimuli

change in environment

positive feedback loop

enhances or amplifies changes

negative feedback loop

dampens or buffers changes

components of feedback loops

receptor (sensor), the control centre, and effectors.

importance of spinal reflex

helps prevent damage and injuries to the body

spinal reflex (reflex arc) sequence

1. stimulus
2. sensory receptor detect change
3. sensory neuron carries signal from receptor to spinal cord
4. interneuron relays signal from sensory neuron to motor neuron
5. motor neuron carries signal to effector cells
6. effector cell causes response

reaction sequence

1. stimulus
2. sensory receptor detects change
3. sensory neuron carries signal from receptor to CNS
4. CNS processes info, makes decision
5. motor neuron carries response signal to effector cells
6. effector cells cause response

reactions

slower, more complex reactions to stimuli

involves brain, spinal cord and peripheral nerves

reflexes

fast, simple, automatic, involuntary responses to stimuli

involves peripheral nerves, often spinal cord (not brain)

alzheimers

caused by gradual dmg to neurons in brain

affects ability to remember + carry out normal activities

increase in blood sugar

1. pancreas receptors detect inc. blood sugar lvl
2. pancreas stimulates, secretes insulin in blood
3. insulin travels to insulin receptors on muscle + liver cells
4. muscle + liver cells remove excess glucose from blood, stored as glucagon
5. blood sugar lvls dec.

decrease in blood sugar

1. pancreas receptors detect dec. blood sugar lvl
2. pancreas stimulated to secrete glucagon into blood
3. glucagon travels to glucagon receptors on muscle + liver cells (target cells)
4. these cells release glucose into blood
5. blood sugar lvls inc.

hormones

chemical messengers used to carry info

endocrine system glands purpose

glands secrete hormones

endocrine system purpose

responsible for growth, repair, digestion, sexual reproduction, homeostasis

what is the hypothalamus made of

nerve tissues

hypothalamus target + main effect

pituitary gland

links nervous system to endocrine

pituitary gland hormones

thyroid stimulating hormone (TSH)

growth hormone

thyroid stimulating hormone purpose

controls rate of thyroxin released

growth hormone purpose

stimulates muscle growth + bone size

adrenaline purpose

prepares body for “flight or fight” response

causes immediate release of energy

estrogen + progesterone functions

female sexual development, maintenance of pregnancy

testosterone functions

male sexual development + activity (sperm)

thyroid gland hormone

thyroxine

thyroxine purpose

regulation of chemical reactions in cells e.g. respiration (metabolism)

pancreas hormones

insulin

glucagon

insulin + glucagon functions

control blood sugar levels

relationship between hypothalamus and pituitary gland

hypothal. constantly checks internal environment. if the conditions change, it responds by secreting hormones to the pituitary gland, which then responds to the information by secreting other hormones or producing fewer.

internal environment

conditions within tissues, organs and systems

type 1 diabetes

pancreas progressively decreases insulin produced until there’s none at all

type 2 diabetes

pancreas makes insulin but cells don’t respond to it as they should (insulin resistance)

1st line of defence + purpose

physical barriers

prevents pathogens from entering body

physical barriers

skin, saliva, eyes (tears), mucus membrane (trap), acid (stomach), reflexes

second line of defence

innate immune response

innate immune response

1. broad response
2. wbc get involved

1. broad response

blood clotting, inflammation, fever

blood clotting

prevents pathogens entering through damaged skin

inflammation

increased no. of wbc reaching infected area (becomes red, hot)

fever

destroys weaker pathogens that can’t handle the heat

2. wbc get involved

* neutrophils


* macrophages

phagocytosis

wbc arrive in blood, eat any foreign substances

neutrophils

phagocytosis, die, become pus

macrophages

phagocytosis, present particles to next defence line

3rd line of defence

adaptive immune response

adaptive immune response purpose

wbc in this line are made to target __specific__ pathogens

wbc in adaptive immune response

* b-cells
* t-cells

b-cells

* produce antibodies
* antibodies fit exactly on specific ptg to prevent spreading + help t-cells

t-cells

attack + destroy specific, recognised pathogens

main pathogens that cause disease

* bacteria
* virus
* parasites
* fungi

bacteria

* single celled, living organisms
* some killable w/ antibiotics
* e.g. necrotising faciitis (flesh eating disease)

virus

* much smaller than bacteria, non-living
* insert selves into cells, use body’s DNA to replicate + spread
* e.g. ebola, covid

parasite

* organism, lives on another host organism
* benefits from nutrients causing harm to host organism
* e.g. malaria

fungi

* caused by fungus
* feed off a protein in skin, nails, hair etc
* red + itchy skin
* most harmless, easily treated
* e.g. ringworm

how are vaccinations made?

made with killed/weakened versions of the disease-causing germs/parts of germs (antigens)

how do vaccinations work?

each pathogen has a specific antibody that acts on it

1st time we’re exposed, our body is slow to make antibodies to fight it

2nd time, antibodies are made much faster + pathogen destroyed because you’re immune

memory cells

* adaptive defence has memory b&t-cells made especially for the disease
* cells remember disease if it enters our body again + kills it very quickly

pathogens

disease causing micro-organisms

disease

anything that causes your body to stop working properly

infectious diseases

diseases that can be spread

contagious diseases

diseases easily spread

→ passed by touching infected person/items touched by them