Brain and Behaviour Part 1 Flashcards
How do simple organisms behave?
They generate a response to a stimulus
How do complex organisms behave?
They have a variety of appropriate responses to depending on the wide variety of stimuli
What is the purpose of the nervous system in humans?
To allow us to interact flexibly with the environment and to select appropriate responses to stimuli
What is the nervous system?
A network of electro chemically active cells or neurons which are specialised to communicate with each other
What are the simplest and most complex forms of NS?
Uncentralised is the simplest, where there is no nerve centre
Centralised is the most complex form, where neurons are clustered near the head (brain like structure) and the scattered neurons around the body are connected to the ‘brain’
what are the subdivisions of the PNS?
Somatic - interprets input of sensory organs
Autonomic - no external input and operates internal organs
Sympathetic - fight or flight response
Parasympathetic - rest and digest/maintenance
What is grey matter?
Highly condensed cell bodies which appear grey under a microscope
What happens in the NS?
sensory signals are detected
signal is interpreted (without the brain)
motor signals are sent
What is the monosynaptic reflex arc?
A one direct connection network between sensory and motor neurons e.g. knee jerk reactions
Describe the process of the monosynaptic reflex:
Remember
Reflexes Are Accurate Signals Allowing Contraction
1) There are receptors inside each muscle fibre
2) These activate sensory neurons
3) Axons enter the spinal cord which connect to a motor neuron
4) Axons split via the ventral root
5) This activates the muscle from which the signal originated
6) Finally causes the muscle to contract
What type of reflex doo monosynaptic reflexes produce?
They produce smooth stable movements rather than quick stretching of skeletal muscles
What is the difference with the polysynaptic reflex arc?
It is more complex as interneurons are involved
What is the process of a polysynaptic reflex?
1) Sensory and motor neurons are connected via interneuron(s)
2) Neurons have multiple synapses between them but they contribute to the same signal and function as one big synapse
3) Receptor and effector are in different locations e.g. step on something sharp and lift up the leg
What is the function of the Medulla and pons?
The hindbrain where the spinal cord becomes the brain
What is the function of the midbrain?
Associated with combining information from different senses and directs our attention
What is the function of the forebrain?
Responsible for higher level functions
What is the function of the Thalamus (diencephalon)?
The large structure on top of the midbrain which is the ‘relay station’ for incoming sensory signals
What is the function of the hypothalamus?
A small structure in front of and below the thalamus. It connects directly to the pituitary gland (the master gland of the endocrine system). Known as the hypothalamic-pituitary connection
What is the function of the cerebrum (telencephalon)?
Receives incoming signals from the thalamus
What is the function of the cerebral cortex?
Layers of neurons which cover the whole of both hemispheres, with cell bodies which send axons to the contralateral hemisphere. Contains clusters of sub cortical nuclei
What is the function of the corpus callosum?
A bundle of nerve fibres which connect the 2 hemispheres, allowing them to communicate
What is the basal ganglia?
A group of nuclei surrounding the thalamus. Closely connected to the amygdala, and associated with motor control
What is the role of the limbic system?
It is crucial in memory and emotion. Includes the amygdala, hippocampus, and fornix. Connects to the hypothalamus and olfactory system
Describe contralateralisation of the hemispheres:
The right side of the body is processed in the left hemisphere and vice versa. The right half of each eye sends signals to the left hemisphere and vice versa.
What is the role of the endocrine system?
Controls the slow and overall coordination of cell activities and secretes hormones into the bloodstream
What signal transmission takes place in the nervous system?
Cells generate electrical impulses which are transmitted with high speed and precision. communication is rapid and constant, which controls/adjusts cell activity
Give some properties of the neuron:
Generate and transmit electricity which travels at high speeds over distances to reach target cells. They need constant oxygen and glucose supply and without they stop working and die in minutes. Neurogenesis completes within 5 months of conception and most neurons cannot be replaced after this.
What is the function of the neuron?
To provide a structured communication network for the nervous system
What are glia cells?
They provide a protected environment for neurons to survive. They develop like neurons from neural stem cells, and there are as many glia as there are neurons in the brain.
What are astrocytes?
They are star shaped cells which provide physical and nutritional support for neurons, such as transporting nutrients from blood vessels to neurons and taking away waste products and holding neurons in place
What are microglia?
Small and mobile glial cells which are constantly moving to defend and aid repair of damaged neurons. They also digest dead neurons
What are oligodendroglia?
Provide myelin (fatty insulation) for axons
What is the role of dendrites?
The input area of the neuron
What is the role of the axon hillock?
The start of the axon
What is the role of the axon terminals?
The end of the axon
What is the role of calcium ion channels?
Located on the presynaptic neuron and open in response to an action potential
Excitatory synapse
More positive ions enter the synapse causing depolarisation (neuron becomes more positive). This increases the likelihood that an action potential being triggered at the axon hillock and the signal being passed on.
Inhibitory synapse
More negative ions enter the synapse causing hyperpolarisation (neuron becomes more negative). This decreases the likelihood of an action potential being triggered at the axon hillock and the signal being passed on.
Action potential
A sudden change in membrane voltage of the neuron. An AP is triggered when the neuron depolarises beyond - 50 mV. Occurs during the rising phase.
Membrane potential
The difference in electrical charge between the inside and outside of the neuron.
What does a neuron at rest look like?
Sodium and chloride ions are more prevalent outside of the cell, and potassium ions are more prevalent inside of the cell. At rest the inside is more negatively charged than the outside.
What is the sodium potassium pump?
A transport protein which is always pumping 3 potassium ions out of the cell and 2 sodium ions into the cell. This keeps the membrane potential negative as there are more positive ions being pumped out than in.
Threshold membrane potential
When the threshold is reached, around - 55 mV, lots of sodium ion channels open allowing positively charged sodium ions into the cell. Membrane potential reaches 0 and then becomes positive causing massive depolarisation (neuron becomes more positive) known as the rising phase
Peak depolarisiaion
Depolarisation reaches the limit causing sodium channels to close and potassium channels to open, allowing repolarisation (the falling phase)
Return to resting membrane potential
After repolarisation where more potassium ions are entering the cell, the neuron returns to resting potential but actually overshoots causing hyperpolarisation (becomes more negative). It is difficult for the neuron to fire when this is happening so the cell returns to resting potential, so potassium channels close and the neuron is ready to be fired again.
Summation
Changes in the post synaptic neuron caused by one action potential isn’t enough for it to fire, so the total input of hundreds of post synaptic neurons must be combined.
Temporal summation = post synaptic potentials received in quick succession
Spatial summation = post synaptic potentials are combined from different synapses in different locations
