B6
- Created by: emchown
- Created on: 09-03-15 17:50
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- B6
- Reflexes
- Organism detect and respond to a stimulus (change in the environment)
- Receptors are stimulated by the stimulus and produce a rapid, involuntary response (Simple Reflex)
- Receptors are stimulated by the stimulus and produce a rapid, involuntary response (Simple Reflex)
- Animals react in a way that will result in survival
- Simple Reflexes in Babies
- Absense of reflexes or failer to disapear my lead to a babies nervous system delevoping incorrecty.
- Stepping Reflex - babies feet on firm surface, walking movements
- Grasping- baby grasps finger when placed in hand
- Sucking - baby sucks on finger when in its mouth
- Startle - baby shoots out arms and legs when startled
- Rooting - baby turns head, opens mouth when cheek touched.
- Adults
- Pupil reflex - bright light makes muscles in iris to contract, retina not damaged.
- Knee-Jerk - when knee struck, leg kicks out.
- Dropping hot object - picking up hot object results in throwing it away.
- Sending Signals
- Hormones
- Insulin (controls blood sugar levels) and oestrogen are secreted in blood.
- Chemical signals are very slow and move to target organs
- Effects last for longer
- Hormones
- Organism detect and respond to a stimulus (change in the environment)
- Detecting Changes
- Animals require presence of one or more receptors to detect stimuli
- Light - receptors in eyes
- Sound - receptors in ears
- Changes of position - receptors in balance in inner ear
- Taste - receptors on tongue
- Snell - receptors in nose
- Pressure - receptors for pressure in skin
- Temperature - receptors for temp. in skin.
- Coordinating Response
- Receptors are connected to the processing centre (spinal cord for simple reflexes) by Sensory Neurons
- The processing centre coordinates a response by sending back an electric impluse through motor neurons to the effector
- Effectors carries out the response - Spinal Reflex Arc.
- Drawing Pin Example:
- 1) A receptor is stimulated by drawing pin (effector)
- 2) This causes impulses to pass along a sensory neuron to spinal cord
- 3) Senesory neuron synapses with relay neuron.
- 4) Relay synapses with motor neuron, sending impulses down it
- 5) Impulses go to the muscles (effectors) and causing them to contract in response.
- Arrangement of neurons into fixed pathway in reflex arc means responses are automatic and quick
- If signal had to travel to brain, response may be too slow
- Receptors and Effectors
- Muscle Cells
- Speciallised cells that make up the tissue are effectors
- Impulses travel along motor neurons and terminate @ muscle cells - causing them to contract
- Light receptors in Retina
- The lens focuses light onto receptor cells in the retina which are sensitive to light
- The receptor cells are stimulated and the optic nerve carries impulses along sensory neurons to the brain
- Hormone Secreting Cells in a Gland
- These cells are effectors
- Activated by an impulse which travels along a motor neuron from CNS and terminates at gland.
- Impulse triggers release of hormone into bloodstream, which transports to required sites
- Muscle Cells
- Structure of Neurons
- Carry electrical signals (nerve impulses)
- Elongated to make connections between parts of body
- Branched endings - allow single neuron to act on other neurons/ effectors
- Motor Neurons
- Cytoplasm forms long fibre surrounded by cell membrane - An Axon
- Some axons surrounded by a fatty sheath
- Insultes neurons from neighbouring cells
- Increses speed of impulses
- Central Nervous System
- Info. from neurons is co-ordinated here
- Made up of brain and spinal cord
- - Receptor- Sensory N- Relay N-Spinal Cord- Bain -Spinal Cord-Motor N- Effector
- CNS connected to body via sensory and motor neurons - Peripheral Nervous System
- PNS sensory and motor neurons transmit messages all over body and to and from CNS
- Synapses
- Gaps between adjacent neurons
- Number in the brain decreases with age - stabilising by adulthood
- impulse reaches end on neuron, triggers release of chemicals - Transmitter Substanses, into synapse.
- Diffuse across synapse and bind with specific receptor on relay neuron membrane
- Transmittter substance reabsorbed by sensory neuron
- By transporter molecules.
- 1) Nerve impulse moves through sensory neuron
- 2) Transmitter substances released into synapse
- 3) T.S bind with receptors on motor neuron
- 4) Nerve impulsesent through motor neuron
- Drugs and the nervous system
- Ecstasy affects transmitter substance - Serotonin
- Serotonin has mood enhancing effects eg. happy
- Ecstasy blacks sites in brains synapses whewre chemical serotonin is removed
- Serotonin concentrations in brain incease and makes people very happy.
- Long term consequence - memory loss
- Cerebral Cortex
- Part of bruan associated with intelligence, memory, language and consciousness
- Variety of Methods to map different regions of the cortex
- Physiological Techniques
- Damage to diff. parts of brain give diff. problems
- Studying effects of accidents/illnesses leads to understanding
- Directly stimulating the brain with electrical impulses leads to an understanding of what parts control what
- Electronic Techniques
- Electroencephalogram (EEG) is a visual record of the electrical activity generated by neurons in the brain
- By amplifying electrical signalspicked up through skull, trace produced showing rise an fall of electrical potentials (Brain Waves)
- Stimulating receptors means parts of brain that respond can be mapped
- Magnetic Resonance Imaging (MRI)
- Technique that produces images of cross sections of the brain
- Computer-generated image uses colour to represent different levels of electrical activity
- Activity in brain changes depending on what the person is doing/thinking
- Physiological Techniques
- Conditioned Reflexes
- Reflex responses to a new stimulus can be learnt
- Body learns to produce a specific response when a certain stimulus is detected
- Works by building an association between the new stimulus (secondary stimulus) and the stimulus that naturally triggers the response (primary stimulus)
- Final response has no direct connection to the stimulus
- Some conditioned reflexes can increase a species chance of survival
- Development of Brain
- Mammels have a complex brain that contains billions of neurons
- Neuron pathways are formed in brain during development
- The way in which the animal interacts with its environment determines what pathways are formed
- Huge variety of pathways = animals easily adapt to new situations
- As each neuron matures, it sends out multiple branches, increasing the no. of synapses
- Each time there's a new experience, different pathways between neurons are stimulated
- Everytime an experience is repeated, the pathway is strengthened
- Pathways not used regularly - deleted
- These modifications mean pathways become more likely to transmit impulses than others and person will become better at task
- Certain tasks are learnt through repetition
- Feral Children
- Neural pathways not used = deleted
- If a new skill not learnt by particular stage in development, person not able to learn it in same way as normal
- Feral children dont go through normal development process - isolated from society
- Child Development
- Milestones that can be checked to see if development is following normal patterns
- If milestones are missing or late it could mean there are neurological problems or child is lacking simulation
- Memory
- Verbal Memory (words and labels) can be divided into Short Term and Long Term memory
- Short-Time - Stores limited amount of info. for limited time (15-30 secs)
- Long-Term - store unlimited amount of info.
- In short term, up to seven seperate pieces of info can be stored
- Capacity can be increased bu Chunking the info. ie. putting it into smaller chunks
- Long term is where info. is stored in brain through repetition which strengthens and builds up neuron pathways
- More Likely to rememeber when:
- Its repeted
- Strong stimulus associated
- Pattern to it
- Memory Models
- Sensory memory lasts 1-2 seconds
- Reflexes
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