Homeostasis - nervous system and the brain

what is homeostasis?

maintaining relatively constant internal conditions - achieved by the nervous system and endocrine system

GIve 3 examples of conditions regulated in the human body

blood glucose levels, body temperature and water levels

what is the function of the nervous system?

enables organisms to respond to changes in their surroundings and coordinate their behaviour

what is the central nervous system made up of?

the brain and spinal cord

what is the peripheral nervous system made up of?

all other nerves

stimulus definition

a change in the external or internal environment; e.g. a change in light intensity or a change in blood glucose concentration

receptor definition

a specialised cell that detects a change in the environment/stimulus; e.g. a rod or cone cell in the retina of the eye

sense/sensory/receptor organ definition

a collection of specialised cells that detect changes in the environment; e.g. the eye

sensory neurone definition

a nerve cell that carries nerve impulses from sensory organs to the CNS

coordinator (CNS) definition

processes information received from receptors via sensory neurones and coordinates the body’s response

relay neurone definition

a nerve cell that carries nerve impulses between a sensory neurone and a motor neurone; found in the CNS

motor neurone definition

a nerve cell that carries nerve impulses from the CNS to an effector

effector (organ)

a muscle or gland; carries out the response to restore optimum levels

response definition

the body’s reaction to a change in the environment

nervous system flow chart

stimulus - receptor - CNS - effector - response (sensory, relay, motor)

what is a neurone?

a nerve cell

what is a nerve?

a bundle of neurones

Why does a motor neurone have many dendrites and many nerve endings?

so it can connect to many other neurones

why does a motor neurone have nerve endings and many mitochondria?

for respiration which releases energy for production and release of neurotransmitter chemicals

Why does a motor neurone have a long axon?

so it can carry impulses over long distances

Why is the motor neurone’s axon surrounded by a myelin sheath?

it insulates the axon and increases the speed of the nerve impulses

how does a muscle respond to receiving nerve impulses via a motor neurone?

contract when they receive a nerve impusle

how does a gland respond to receiving nerve impulses via a motor neurone?

secrete a chemical, e.g. a hormone, when they receive a nerve impulse

what is a synapse?

a junction between two neurones

How is a nerve impulse transmitted between one neurone and the next?

A nerve impulse arrives at the end of the first neurone. Neurotransmitter chemicals are released from the first neurone into the synapse. Neurotransmitter chemicals pass across the synapse by diffusion and bind to receptors on the membrane of the second neurone and initiate a nerve impulse

What happens to the neurotransmitter after the nerve impulse has been transmitted to the next neurone?

it gets destroyed

conscious response definition

uses the conscious parts of the brain

unconscious response definition

does not involve the brain (only the spinal cord) OR uses the unconscious part of the brain; called reflexes

what is a reflex action?

rapid, automatic (unconscious) responses. Some protect organisms from damage

reflex action examples

breathing, knee jerk, withdrawal, gag, pupillary, blinking, salivating, moving food through the digestive system

what is a reflex arc>

the route/pathway taken by nerve impulses through the nervous system to bring about a reflex action

describe and explain the path of a nerve impulse in a reflex arc

the receptor detects the stimulus and generates a nerve impulse which is carried along the sensory neurone from the receptor to the CNS. the nerve impulse reaches a synapse at the end of the sensory neurone so neurotransmitter chemicals are released and passed across junction so triggers nerve impulse in the relay neurone. the relay neurone carries the nerve impulse across the CNS to a motor neurone. the motor neurone carries the nerve impulse to an effector. the effector carries out a response

What makes a reflex action so rapid?

the nerve impulse doesn’t have to go through the conscious part of the brain. the nerve impulse only has to travel long 2/3 neurones if in brain as their is no relay neurone and it only has to cross ½ synapses, which slow down the transmission

why is the brain so complex?

it is made up of billions of interconnected neurones and there are 1,000 trillion synapses

cerebral cortex

involved in memory, conscious thought, language and intelligence

cerebellum

coordinates muscular activity and is involved in balance

medulla

coordinates unconscious activities such as breathing, movements in the gut (peristalsis) and changes in heart rate

Why is homeostasis important?

To maintain optimum conditions for enzyme action and all cell functions

What are the methods used by neuroscientists to map regions of the brain to particular functions?

1. Studying patients with brain damage - observe symptoms/changes in behaviour to indicate function of damaged region

2. Electrically stimulating different parts of the brain - observe effects on behaviour in live patients to indicate function of stimulated region

3. Using MRI scanning techniques - observe which parts most active during different activities to indicate region linked to activity

What are the difficulties of investigating brain function and treating brain damage and disease?

Brain is very delicate - surgery may cause unintended damage to another area

Brain is very complex - difficult to work out exactly which parts carry out specific functions

How is information passed along neurones?

As electrical impulses