Chapter 2.1 & 2.2

Multi Cellular Organisms:

• Cells make up tissue

• Tissue form organs

• Organs are part of systems

• Systems make up an organism

Multi Cellular Organisms → Systems → Organs → Tissues → Cells

Cells: The smallest structural unit of living organisms

Organs: Different types of tissues grouped together to perform a particular function

System: Different organs working together to achieve a specialized function to keep an organism working.

Tissue: A collection of similar cells that perform a particular function.

Homeostasis:

• The maintenance of your constant internal environment, this includes temperature, pH, glucose and water.

• Any change (stimuli) in the internal environment needs to be detected (by receptors) so the body can respond.

• If a response is required this needs to be communicated to effectors, so a change can be made so the internal environment can be returned to normal.

Stimulus-response model:

Stimulus → Receptor → Control Centre → Effector → Response

Stimuli: anything your body needs to respond to. This can be external e.g. something dangerous or it can be internal e.g. blood sugar.

Receptors: Identify changes inside or outside the body. There are different specialized receptor cells in different body parts, e.g. photoreceptors in the eye detect light, and thermoreceptors in the skin detect temperature.

Control Centre:

• Once the stimulus is detected by the receptor a message is sent from the receptor to the brain.

• The brain is the control center.

• Here the message is processed, and the brain then decides how best to respond.

• Then a message is sent to the effector.

Effectors: receive messages from the brain e.g. muscles or glands. Give the body’s response to the original stimulus e.g. if you are hot sweat glands produce sweat.

Stimulus → Receptors → Sensory neuron → Relay Neuron → Brain → Motor neuron → Effector → Response

e.g. Heat from the sun → Thermoreceptor → Brain → Effector glands → Body sweats

Types of Feedback:

Negative Feedback: Something that will go up and down and try to stay in an optimal range. e.g. blood pressure, body temperature.

Positive feedback: Only decreases/Increases and will have more and more or less and less. e.g. childbirth, ovulation.

Glucose & Negative Feedback:

• regulating glucose (blood sugar levels) in your body involves negative feedback.

• If an increase of glucose is detected the pancreas responds by releasing insulin.

• Insulin triggers the liver to uptake glucose and store it for later.

This then lowers the blood glucose levels.

Stimulus (increase in blood glucose level) → Receptor (chemoreceptor) → Control Center → Effector (Pancreas) → Response (Insulin released and triggers glucose uptake from cells and storage as glycogen)

Chapter 2.3 - Nervous System

Nervous system: responsible for all we think, do, and feel.

3 Main functions:

• receive information

• process information

coordinate a response to information

• Essentially the nervous system is the body’s communication system

• It allows messages to travel all over the body

• Messages will either be sent from:

  • the body to the brain

  • the brain to the body

• Made of special cells called neurons

2 Parts of the Nervous System:

• central nervous system - made of the brain and spinal cord

• peripheral nervous system - made of all other nerves in the body

Neurons - specialised cells:

• specialised cells that make up the nervous system as called neurons

• join together to make nerves

• these nerves pass messages all around the body

Parts of a Neuron:

Dendrite: receive messages from other neurons and pass the message on to the soma

Soma: Cell body, contains the nucleus

Nucleus: Cell control centre

Axon: carries electrical message from the soma to the axon terminal

Axon terminal: The end of the axon, release chemicals called neurotransmitters, into the synapse

Synapse: The space between neurons.

Why is there space between neurons?

• neurons do not touch, instead there is a space called the synapse between neurons.

• Because they don’t touch they need something to cross the spare (synapse) between them.

• Chemicals called neurotransmitters cross the synapse and communicate messages from one neuron to the next.

Electrochemical messages:

• messages in the nervous system are called electrochemical messages, this is because:

  • Inside the neuron the messages travel as an electrical impulse

  • Outside the neuron the message travels as chemicals called neurotransmitters.

Stimulus → Dendrite → Cell body (nucleus) → Axon

Types of neurons:

• sensory neurons

• motor neurons

• interneurons

Sensory Neurons:

• carry messages from the body to the brain

• Takes messages from the 5 senses to the brain to be processed

Motor Neurons:

• Carry messages from the brain to the body, including muscles

• Muscles then move and respond

Interneurons:

• Only found in the central nervous system (brain and spinal cord)

• Connect with sensory neurons and motor neurons in the peripheral nervous system

• Carry messages up and down the spinal cord and in the brain

Reflex actions:

• Your response is faster than normal because the message to move away does not come from your brain but rather from your spinal cord

Reflexes Response:

Message received at the senses → Messages travel along sensory neurons to spinal cord, connects with interneurons → Interneurons in spinal cord detects danger → Interneurons sends message along motor neurons to muscles → Muscles move to get away from danger

Summary:

Normal Concious Response:

• Sensory neurons

• to interneurons in spinal cord

• to brain

• to interneurons in spinal cord

• to motor neurons

Reflex:

• sensory neurons

• to interneurons in spinal cord

• to motor neurons

Chapter 2.4 - Getting the message

Sense Organs:

• sense organs are used to detect stimuli ( such as light, sound, touch, taste and smell) in your environment

• Examples of human sense organs are your eyes, ears, skin, tongue and nose

• These sense organs contain special cells called receptors

Types of Receptors:

Thermoreceptors - Temperature

Mechanoreceptors - Pressure

Chemoreceptors - Nose and Taste buds

Photoreceptors - light

Noiciceptors (pain receptors) - pain

Touch: Skin contains - pain receptors, mechanoreceptors, thermoreceptors

Smell: The nose contains chemoreceptors that send a message via the olfactory nerve to the brain

Taste: Chemoreceptors in the tongue recept taste

Chapter 2.5 - The brain

3 Main Parts:

• Forebrain

• Midbrain

• Hindbrain

Hindbrain:

• Connects the spinal cord and the brain

• Responsible for:

  • Breathing

  • Basic movement

  • Balance

Midbrain:

• sits in the middle

• helps regulate alertness (from being fully awake of deeply asleep)

• Some reflexes (sneezing and coughing)

Forebrain:

• Contains:

  • Cerebrum (including the cerebral cortex): thinking and planning

  • Thalamus: filters sensory information

  • Hippoampus: creates new long term memories

Cerebrum:

• the largest part of the brain

• responsible for thinking, planning and voluntary movement

• divided into two hemispheres

• each hemisphere is made of 4 lobes

• cerebral cortex is 2-3mm thick

Hemispheres:

• the cerebrum is divided into 2 halves called the left and right hemispheres

• the 2 hemispheres are joined by a bridge of nerves called the corpus callosum. this is how the two halves communicate.

Left Hemisphere:

• logic

• language

• maths

• analysis

• reasoning

• controls the right side of the body

Right Hemisphere:

• creativity

• expression

• emotion

• imagination

• facial recognition

• controls the left side of the body

4 Lobes: (there are 8 lobes in total, 4 in each hemisphere. e.g. left frontal lobe)

Frontal - movement

• problem solving

• emotional traits

• reasoning (judgement)

• speaking

• voluntary motor activity

Parietal - sensation of touch

• knowing right from left

• sensation

• reading

• body orientation

Occipital - vision

• vision

• colour perception

Temporal - sound/hearing

• understanding language

• behaviour

• memory

• hearing

Cerebellum:

• balance

• coordination and control of voluntary movement

• fine muscle control

Brain stem:

• breathing

• body temperature

• digestion

• alertness/sleep

• swallowing

Chapter 2.6 - Endocrine System

Hormones:

• your nervous system is not the only means of controlling and coordinating activities in your body

• your endocrine system uses chemical messengers called hormones

• hormones are made by glands and released into your blood stream

• only particular cells will respond to hormones, these are called target cells and they are receptors for those hormones

Hormones control functions such as:

• growth

• metabolism

• development

• sexual reproduction

• stress

Pituitary Gland:

• in the brain

• controls many other endocrine glands

  • thyroid

  • ovaries/testes

• Influences: water balance in the body, growth

Hypothalamus:

• in the brain

• sends hormones to the pituitary gland to control its release of hormones to the other endocrine glands

• influences temperature, growth, appetite, sensation of pain and pleasure

Pineal Gland:

• in the brain

• produces melatonin

• controls body’s sleep wake cycle

Pancreas and insulin:

• insulin is a hormone

• it is secreted by your pancreas when you have high blood sugar

• insulin works on target cells in your liver

• your liver then absorbs more glucose

• this then lowers your blood sugar

• this is an example of negative feedback in action

Pancreas and Glucagon:

• glucagon is a hormone

• it is secreted by your pancreas when you have low blood sugar

• target cells in your liver

• glycogen is broken down to form glucose

• glucose then increases your blood sugar levels

• this is an example of negative feedback

Insulin:

• hormone

• secreted by pancreas

• works with liver

• decreases blood sugar levels

Glucagon:

• hormone

• secreted by pancreas

• works with liver

• increases blood sugar levels

Chapter 2.8 - The Brain and Emotions

The 6 basic emotions:

• happiness

• sadness

• fear

• disgust

• anger

• surprise

Limbic System:

• the limbic system is made up of a collection of structures within your brain

• the limbic system is involved in:

  • memory

  • controlling emotions

  • decision making

  • motivation

  • learning

Parts of the brain involved with emotion:

• thalamus

• hypothalamus

• hippocampus

• amygdala

Fight or flight response: when you feel angry, your hypothalamus responds by sending messages to your pituitary gland to instruct your adrenal glands to release adrenaline.

• this hormone acts to

  • increase your heartrate

  • dilate your pupils

  • constrict skin blood vessels

  • shut down digestion

Amygdala:

• your fight or flight response originates in your amygdala

• it is this tiny part of your limbic system that decides the emotional value of what is happening

• it may sense a particular facial expression or tone as being threatening, or it may detect an event that was previously tagged as being a negative experience

Brain Chemistry:

• neurotransmitters are chemicals involved in passing messages between your neurons

• within your brain, there are many neurotransmitters that influences how you feel and react

  • serotonin

  • noradrenaline

  • dopamine

Noradrenaline:

• noradrenaline can act like the accelerator

• it can promote alertness, better focus and concentration

• your brain also needs this chemical to form new memories and to transfer them to your long term storage

Serotonin:

• acts like the brakes on your emotions

• it can produce a calming effect and is important for maintaining a good mood and feelings of contentment

• it also plays a role in regulating memory, appetite and body temperature

• low levels of it can produce insomnia, depression and aggressive behaviour

Dopamine:

• is important for healthy assertiveness and happiness

• dopamine levels can be depleted by stress or poor sleep

• too much alcohol, caffeine and sugar may also lead to reduced dopamine activity in your brain