term 1: psychology - school notes

Homeostasis

Coordination in a multicellular organism

• Coordination is the way all the organs and system of the body are made to work efficiently together

• Cells of multicellular organisms cannot survive independently.

• They depend on each other and work together

• This requires organisation, coordination and control

Multicellular organisms contain systems contain organs contain tissues contain cells

Homeostasis

• Your body systems need to work together so that a comfortable stable environment (temperature, pH, concentration of ions etc) for the cells is maintained

• This is achieved through homeostasis

• homeostasis - maintenance of the constant internal environment

• To stay alive and well, the body needs to be able to detect change in the internal and external environment, and respond ina an appropriate way

Without homeostais we would:

• Run out of useable energy

• starve

• swell up and have our cells burst

• dehydrate

• suffocate

• THe coordinatino of our body systems is integral to homeostasis and homeostasis is essential for life

The stimulus response model

• To achieve homeostasis (balance), the body needs to respond to changes within the body’s internal and external environment

• these are detected by receptors within a body and if a response is required then action are bought about by effectors to bring the body back to equilibrium

• this process can be explained via a stimulus response model

Stimulus

• A stimulus is any change in the internal or external environment

Receptor

• Receptor: special type of nerve cells that may be located in sense organs. Different type of receptors respond to particular stimuli

• Receptors identify changes inside and outside your body

Control centre

• Control centre: specialised cells that are locating within the brain and spinal cord

• It receives, processes the information from the receptor, then determines an appropriate response that is sent to the effector

Effector

• Effector: a Muscle or gland that receifes the message from the central nervous system to respond in a particular way

• Their response depends on the original stimulus

Homeostasis and feedback

Types of feedback

• Negative feedback

  • Most common

  • Aims to reduce the stimulus

    • Homeostasis is achieved by negative feedback loops

    • Receptors detect a change in the internal enviornment and effectors work to revers the direction of the change to achieve equilibrium

    • Starts at a anormal range, goes beyond normal rand and then returns to normal

    • e.g: glucose regulation, temperature regulation, blood pressure and blood pH

• Positive feedback

  • Uncommon

  • Aims to INCREASE the stimulus (take away from homeostasis)

  • e.g: child birth

The NErvous system

• The nervous system: A complex, highly organised network os specialised cells that enables the brain to receive information about what is going on from both inside and outside the body and to respond appropriately

• The nervous system controls how you sense, feel, think and do

• This also includes your involuntary responses such as breathing, heart rate, feeling “butterflies“ in your stomach

3 main function

• Receive information

• Process information

• Coordinate a response to information

Central VS Peripheral Nervous System

• THe nervous system is compesed of

  • Central Nervous System (CNS)

  • Peripheral nervous system (PNS)

• These systems are both made up of nerve cells called neurones

THe brain

• THe brain is an intricate network of cells

• also known as the control centre

• Processes sensory information receive from the body and respond by controlling all bodily functions and actions

• Responsible for virtually everything we, think and feel

The spinal cord

• THe spinal cord is a long, thin bundle of nerve tissue that extends from the base of the brian to the lower back

• Receives sensory information from the body (ie. the peripheral nervous system) and send these to the brna from processing

• Receives motor information from the brain and send it to relevant parts of the body to control muscles, glands and internal organs so that appropriate actions can be taken

Damaged SPinal Cord

• When the spinal cord is injured, the brain loses both sensory input from and control over the body

• The higher up on the spine the injury is, the greater the number of nerve connections between the brain and the body that are being severed

Neurone

• Neurone: indivuidual nerve cells

• Building blocks of the brian and nervous system

• All neurones have 3 basic functions

  • receive information

  • Process information (to determine whether or not the information should be passied along)

  • Communicate information to target cells (toerh neurones or muscles or glands)

Tyoes of nuerones

• Neurones have sepcialised functions and vary in shape and size. Three types of nuerones

• sensory neurone

  • Speicalise in sending sensoryin information to the cns

• Motor neurone

  • Specialise in sending motor information from the cns

• Interneurone

  • serve as communication links between neurones

Soma

• also known as the cell body

• Nuclues of the neurone is found in the soma

• Controls the cell functions and produces proteins of the cell

• Appendages or potrusions that extend from the cell body are known as processes. two types of processes:

  • dendrites

  • axons

Dendrites

• Longer processes extending from the cell body

• Specialised to transmit action potentials (ie neural information)

• Towards the end, the axon spilts into many branches known as axon terminals

  • THese axon terminals make connections to target cells

Myelin Sheath

• Made of fat and protein - act like unculation on electrical wire

• helps speed up transmittion of nerve impulse down a long axon and protects the neurones

• Not found on denderites, only on axons

• Myelinated neurones are typically found in the perioheral nerves (sensory and motor neurones), while non-myelinated neurones are found in the braina and spinal cord

• Myelin sheaths - produced by Schwann cells

• Nodes of Ranvier - gaps in the myelin sheath

Summary of all the parts

Multiples Sclerosis

• Multiple sclerosis: an autoimmune disease, where the body mistakenly attacks the brain and spinal cord

• It does this by damaging myelin - the protective coating around the nerves. When myelin is damaged, messages can no longer be clearly transmitted from the brain and spinal cord to other parts of the body

Symptoms include:

• Problems with motor (muscle) control

• Visual problems

• Problems with coordination and memory loss

The axons of neurones group together to form nerves

Sensory neurones

• Also known as afferent neurones

• Carry impulses from sense organs to spinal cord and brain (CNS)

• Receives message about a change in the external or internal environment and transmits the information to the interneurone in the CNS

Interneurone

• Located ONLY IN THE CNS and carry signal from a sensory neurone to a motor neurone

• Connect sensory and motor neurones

• Processes impulses in the brain and spinal cord

Reflex

• Some actions need to be carried out very quickly - as a matter of survival

• The message does not have to go to the brain

• This type of pathway, which involves only a few neurones and travels only to and from the spinal cord, is called a reflex arc

Communication between Neurones

• Once the information has reached the axon terminals of the neurone, the message has to be relayed to an adjacent neurone

• This relay of information is in the form of chemical transmission at the synapse

• When the nerve impulse reaches the axon terminals, tiny vesicles containing chemicals called neurotransmitters are transported to the cell membrane of the neurone

• These chemicals are then released into the synapse

• The neurotransmitters move across the synapse and bind to receptors on the membrane of the dendrites of the next neurone

• this may result in triggering the receiving neurone to convert the message into a nerve impulse and conduct it along its length

Piecing it Together

• Your nervous system involves the use of both electrical signals and chemical signals

Learning and memory

• Learning: Gaining/acquiring new knowledge of skills

• Memory: The expression of what you have acquired, ie retaining and retrieving that knowledge/skill

• The existence of memory is evidence that leaning has occurred

• If no learning occurs there is nothing ro remembers

• Leaving would have no value if we could not remember - we usually learn with the understanding that at some future time, we will be able to recall what we have learned

• Learning the acquisition of new knowledge or skills through study, experience or being taught

Memory

• memory is an internal record of prior experience

• Memory is the processing, storage and retrieval of information acquired thorough learning

Memory in not a single thing or precess lovated in one specific area of the brain

We do not have a memory - we have multipls memory systems

Fundamental processes of memory

• Psychologists have devised a number of models to describe and explain human memory

• Despite differences in all the models, all models can be simplified to involve three fundamental processes

• Boxes represent components

• arrows represent movement of information

• All 3 stages of memory occur as a sequence

• They interact and are interdependent

Fundamental processes of memory

• A simplified representation of the 3 fundamental processes required for human memory

• If any of these processes fails, memory will fail

• Encoding: Information is converted for storage

• Storage: Information is retained in memory

• Retrieval: Information is recovered from memory when needed

This is the Atkinson - Shiffrin Model

Chunking

• Chunking is a term referring to the process of taking individual pieces of information (chunks) and grouping them into larger units

• Give some examples where chunking is commonly used to help us remember things in everyday life

• Human working memory has a capacity 7 (+/- 2) items 0. chunking allows us to hold more information and thus increase our capacity

Extra info:

What is Homeostasis?

• The internal environment in which your cells are bath in to be kept constant.

• Variable that need to be maintained within set limits include:

  • Temperature

  • pH

  • Blood glucose levels

  • Carbon Dioxide

  • Water

• Homeostasis: The maintenance by an organism of a constant internal environment

Detecting stimuli

• Stimulus: The trigger that leads to a response

• Receptors: cells which detect a change

• Detecting changes in our environment requires the use of our sense organs

Receptors in the skin

• Stimulus: Pressure and temperature

• Receptors: mechanoreceptors and thermoreceptors

• Mechanoreceptors: A specialised sensory cell that detects physical touch, pressure, stretching, or other mechanical stimuli, essentially acting as a "touch sensor" in the body, sending signals to the nervous system when it experiences these physical forces; like feeling something on your skin or sensing muscle tension. 

• Thermoreceptors: Specialised parts of neurones, or nerve cell endings, that give the body the ability to detect changes in temperature. these kick in when the body temp above 37.5 or below 35.8

Pain receptors

The Nervous System

Human nervous system

• Communication system that controls all parts of your body

• There are 2 main parts

  • Central nervous system

  • Peripheral nervous system

Central nervous system

• Brain and spinal cord

• Receives information from all over the body

• Processes all information

• Sends messages telling the body how to respond

• Think of it as the central pentagon

Peripheral Nervous Sysytem

• Made up of nerves that carry messages to and from the central nervous system and other parts of you body

• It also regulates involuntary bodily functions

• think of it as a messenger going on, on the side

Stimulus response model

Reflex Action

• When you touch something very hot or sharp you automatically pull your hand away

• This reaction is called a reflex action

• Reflex actions are:

  • Involuntary

  • Very fast

  • Where the message travels to the spinal cord and back

  • Protects you from danger

Synapse: The place where neurones (information messengers) connect and communicate with each other

Neurons

• The nervous system is made up of trillions or neurones (nerve cells)

• They carry electrical messages (nerve impulses)

Nerve Impulses

• Nerve impulses are very high speed

• The message travels one direction

• They travel in response to a stimulus a serve to transmit a record of sensations from the receptor or an instruction to act as an effector

A nerve is made up of a large number of neurones, each neurone is surrounded by a myelin sheath

Parts of the neurone

• Axon: Carries nerve impulses away from the cell body

• Dendrites: highly branched to ‘catch‘ and carry messages into cell body

• Myelin sheath: fatty material that provides insulation and protection to axon and speeds up nerve impulses

• Node of Ranvier: Gaps in the myelins sheath where impulses can ‘jump‘ from node to node.

• Schwann cell: forms myelin sheath

• Neurilemma: Helps repair injured fibres

• Axon terminals/motor end plate: stores and transmits neurotransmitters

Synapse

• When an impulse reaches the axon terminal a chemical called neurotransmitter is release into the synapse (gap between neurones or neurone and effector)

• A neurotransmitter is a signalling molecule released from the axon terminals into the synapse between nerve cells (neurones)

1. Dendrites receive message

2. Bring into the cell body. It travels down the axon and reaches axon terminals

3. Chemicals called neurotransmitters are released

4. It crosses the synapse (space between 2 neurones)

5. The neurotransmitters attach to receptors on the dendrites of the neurone

6. The message is passed on

3 types of Neurones

• Motor neurone: Carry messages FROM central nervous system to effectors (muscles and glands) (motor to the muscles/glands to tell them what to do)

• Sensory neurone: Carry messages TO the central nervous system from sense organs (sense whats going on and say something)

• Connector neurone/Interneurone: Link between sensory and motor neurones (found a lot in the spinal cord)

• The longest neurone in your body extends from your big toe to the middle of your spine - almost a metre long

Reflex responses

• Rapid and unconscious (involuntary) nervous response

• Message does not go all the way to brain first

• Will go to closest point on the central nervous system - spinal cord

• Allows you to response before detecting the pain

• Very simple pathway

• Protects you from danger

The Brain

The human brain

• approximately 75% water

• approximately 100 billion nerve cells

• Volume: 1200 - 1400ml

• Highly convulted (folds and creases) which means it has a greater surface area

Parts of the brain

• Cerebrum: conscious thought, voluntary movement, thinking, learning, memory, decision-making, perception of the senses

• Cerebellum: fine coordination of muscle movement and the control of posture and balance

• Medulla Oblongata: Heart rate breathing rate and diameter of blood vessels.

• Hypothalamus: Body temperature, sleep patterns, heart rate, food and water intake

Internal environment

• Complex organisms control internal environment within narrow ranges, including

  • Body temperature

  • Levels of chemical in the blood and tissues (e.g. glucose, oxygen, carbon dioxide, water and ions)

  • Blood volume

  • Blood pressure