paper 2 - biopsychology Flashcards
The nervous system
The nervous system is specialised network of cells in the human body and primary internal communication system.
It is based on electrical and chemical signals.
The nervous system has two main functions, what are they?
-To collect, process and respond to information in the environment.
-To co-ordinate the working of different organs and cells in the body.
Name the two subtypes, the nervous system is divided into.
Central nervous system (CNS)
Peripheral nervous system (PNS)
The central nervous system (CNS)
The CNS is made up of the spinal cord and the brain.
It acts as the body’s control centre, processing sensory information and directing responses. The CNS coordinates voluntary activities like movement and involuntary ones such as breathing and heartbeat.
The brain
Our brains have two main functions; controlling behaviour and body’s psychological process. However, the brain cannot do this alone as it needs to receive information from the body’s sense receptors, which is achieve through communication with the spinal cord.
The spinal cord
The spinal cord is an extension of the brain, it passes messages to and from the brain and connects the nerves to the peripheral.
It’s also responsible for reflex actions such as pulling your hand away from a hot plate.
The peripheral nervous system (PNS)
The PNS transmit messages via million of neurones (nerve cells). It passes messages to and from the central nervous system.
Helps the body to respond to stimuli and regulate various psychological processes.
The peripheral nervous system is divided into the…
Autonomic nervous system (ANS) and somatic nervous system (SNS)
Autonomic nervous system (ANS)
ANS governs the vital functions in the body such as breathing, heart rate, digestion , sexual arousal and stress responses.
Somatic nervous system (SNS)
SNS governs muscle movement and receives information from sensory receptors.
The AUTOMATIC SYSTEM is up-subdivided into the…
Sympathetic nervous system and parasympathetic nervous system.
The sympathetic nervous system
The sympathetic nervous system increase bodily activity (triggers the flight and fight response).
-heart rate increases
-breathing increases
-public dilate
-digestion suppresses.
The parasympathetic system
The parasympathetic system decreases bodily activity ( triggers ‘rest and digest’ response )
-heart rate goes down
-breathing decreases
-digestion decreases
The endocrine system ( glands and hormones)
The endocrine system works alongside the nervous system to control vital function in the body.
The endocrine system acts more slowly nervous system but very widespread and powerful effects.
Glands and Hormones
Various glands in the body such as the thyroid gland, produces hormones. Hormones are secreted into the bloodstream and affect any cell in the body that has a receptor for that particular hormone. The effect will be linked to either growth, metabolism or reproduction.
Hormones helps to regulate bodily functions.
How many glands are there?
7 glands in total
Pituitary gland, hypothalamus, pineal gland, thyroid gland, adrenal gland, ovaries, testes.
Pituitary gland - functions of gland and hormones
Master gland that controls other glands as well, as realising ACTH during the stress response and oxytocin during childbirth.
Hypothalamas
stimulates and activates the pituitary gland.
Pineal gland
release melatonin to control biorhythms such as the sleep-wake cycle.
Thyroid gland
release thyroxine to control metabolism.
Adrenal gland
Adrenal medulla releases adrenaline/ noradrenaline in flight or fight. Adrenal cortex releases cortisol in chronic stress response.
Ovaries
regulates the menstrual cycle and pregnancy by releasing oestrogen.
Testes
produce testosterone for male sex characteristics and muscle growth.
Endocrine and ANS working together: fight or flight
The endocrine system and the autonomic nervous system work along each other during the flight or fight response (stressful event).
Fight or flight response
When a stressor (event that causes stress) is perceived the first thing that happens is a part of the brain called the hypothalamus activates the pituitary gland and this triggers activity in the sympathetic branch (increase bodily activity) of the autonomic nervous system. The ANS (autonomic nervous system) changes from its normal resting state (the parasympathetic state) to the physiologically aroused sympathetic state.
The stress hormone adrenaline/noradrenaline is release from the ADRENAL MEDULLA into the blood stream. Adrenaline triggers physiological changes in the body (e.g increased heart rate) which creates physiological arousal necessary for flight and fight response.
All of this happens in an instant as soon as the threat is detected. This is an acute response and an automatic reaction in the body. The physiological change associated with this sympathetic response are increased heart rate, dilated pupils, increase breathing rate. These changes explain why stress, panic or even excitement are often experienced as ‘sick’ feeling.
Finally once the threats has passed, the parasympathetic nervous system returns to its resting state. The parasympathetic branch of the ANS works in opposition to the sympathetic nervous system- the actions are antagonistic (hostile) to the sympathetic system. The parasympathetic system acts as a ‘brake’ and reduce the activities in the body that were increased by the actions of the sympathetic branch- also referred as the rest and digest response.
SYMPATHETIC STATE
Increases heart rate.
Increases breathing rate.
Dilated pupils
Digestion suppressed.
Contacts rectum
PARASYMPATHETIC SYSTEM
Decreases heart rate.
Increases breathing rate
Constricts pupils.
Stimulates digestion.
Relaxes rectum.
Neurons - neurons and synaptic transmission
Neurones are the basic building blocks of the nervous system; neurones are nerve cells that process and transmit messages through electrical and chemical signals. By transmitting signals electrically and chemically, these neurones provide the nervous system with its primary means of communication.
Types of neurons
Sensory neuron, relay neurons, motor neurons
Sensory neurone
carry messages from the PNS to the CNS. They have long dendrites and short axons.
Relay neurone
Relay neurone- these connects the sensory to the motor neurones or other replay neurones. They have short dendrites and short axons.
Motor neurone
these connect the CNS to effectors such as muscles and glands. They have short dendrites and long axons.
The structure of neurones
Neurones vary in size from less than a millimetre to up to a metre long, but all share the same basic structure.
The cell body includes a nucleus, which contains the genetic material of the cell. Branch like structures called dendrites protrude from the cell body. These carry nerve impulses from neighbouring neurones towards the cell body.
The axon carries impulses away from the body down the length of neurone.
The axon is covered in a fatty layer of myelin sheath that protects the axon and speeds up electrical transmission of the impulse. If the myelin sheath was continuous this would have the reverse effect and slow down the electrical impulse.
Thus, the myeline sheath is segmented by gaps called nodes of ranvier. This speeds up the transmission of the impulse by forcing it to ‘jump’ across the gaps along the axon.
Finally, at the end are terminal buttons that communicate with the next neurone in the chain across the gap known as the synapse.
Location of neurones
The cell of bodies of motor neurones may be in the central nervous system (CNS) but they have long axons which form part of the peripheral nervous system (PNS) .
Sensory neurones are located outside of the CNS, in the PNS clusters known as ganglia. Relay neurones make up 97% of all neurones and most are found within the brain and the visual system.
Electrical transmission- the firing of a neurone
When a neurone is in a resting state the inside of the cell is negatively charged compared to the outside.
When a neurone is activated by a stimulus, the inside of the cell becomes positively charged for a split second causing an ACTION POTENTIAL to occur.
This creates an electrical impulse that travels down the axon towards the end of the neurone.
CHEMICAL TRANSMISSION- chemical transmission
Neurones communicate with each other within groups known as neural networks. Each neurone is separated from the next by an extremely tiny gap called the synapse.
Signals within neurones are transmitted electrically. However, signals between between neurones are transmitted chemically across the synapse.
When an electrical impulse reached the end of the neurone (the presynaptic terminal) it triggers the release of neurone transmitters from tiny sacs called synaptic vesticles.
NEURONE TRANSMITTERS- synaptic transmission
Neurones transmitters are chemicals that diffuse across the gap to the next neurone in the chain.
Once the transmitter crosses the gap, it is taken up by a post synaptic receptor site on the dendrites of the next neurone (axon takes signals to the synapse, dendrites take signal away).
Here, the chemical message is converted back into electrical impulse, and the process of transmission begins again in another neurone.
Several dozen types of neurotransmitters have been identified in the brain (as well as in the spinal cord and some glands).
Each neurotransmitter has its own specific molecule structure that fits perfectly into the postsynaptic receptor site, similar to the lock and key.
Why is direction of travel only one way?- neurone transmitters
The direction of travel can only be one-way. This is because neurotransmitters are released from the presynaptic neurone terminal and received by the post-synaptic neurone (at receptor sites)
Explain excitatory and inhibitory
Neurone transmitters have either an excitatory or inhibitory effect on neighbouring neurone.
For instance, the neurotransmitters serotonin causes an inhibition in receiving neurone, resulting in the neurone becoming more negatively charged and less likely to fire.
In contrast, adrenaline (an element of stress response which is both a hormone and a neurotransmitter) causes excitation of the postsynaptic neurone by increasing its positive charge and making it more likely to fire.
EXCITATION
when a neurotransmitter, such as adrenaline, increases the positive charge of the postsynaptic neurone. This increases the likelihood that the post-synaptic neurone will pass on the electrical impulse- making more likely to fire.
INHIBITION
when a neurotransmitter, such as serotonin, increases the negative charge of the post synaptic neurone. This decreases the likelihood of that postsynaptic neurone will pass on the electrical impulse- making it less likely to fire.
SUMMATION
Whether a postsynaptic neurone fire is decided by the process of summation. The exhibitory and inhibitory influences are summed: if the net effect is inhibitory, it is less likely to fire. If the net effect is exhibitory, It is more likely to fire. I.e the inside of the postsynaptic neurone momentarily becomes positive charged. Once the electrical impulse is created it travels down the neurone.
Therefore, the action potential of the postsynaptic neurone is only triggered if the sum of exhibitory and inhibitory signals at any one time reaches the threshold.
