Biopsychology Flashcards
Central nervous system
- consists of the brain and spinal cord.
- controls behaviour and the regulation of the body’s physiological processes.
Brain
The brain is divided into four main areas:
Cerebrum – largest part of the brain. Four lobes, two halves, called the right and left hemisphere.
Cerebellum - Responsible for motor skills, balance and coordinating the muscles to allow precise movements.
Diencephalon - Contains the thalamus (regulates consciousness, sleep and alertness) and the hypothalamus (regulates body temperature, stress response and hunger and thirst).
Brain stem - Regulates breathing and heart rate.
The spinal cord
The main function of the spinal cord is to relay information between the brain and the rest of the body. This allows the brain to monitor and regulate bodily processes, such as digestion and breathing, and co-ordinate voluntary movement. The spinal cord is connected to different parts of the body by pairs of spinal nerves, which connect to specific muscles and glands. If the spinal cord is damaged, body areas connected to it by nerves below the damage will be cut off and stop functioning.
Peripheral nervous system
The Peripheral Nervous System (PNS) consists of the nervous system throughout the rest of the body (e.g. not the brain or spinal cord). The PNS transmits messages via neurons (nerve cells) to and from the CNS. The PNS has 2 divisions: The somatic nervous system and the autonomic nervous system.
Somatic nervous system
The somatic nervous system controls voluntary movements and is under conscious control. It connects the senses with the CNS and has sensory pathways AND motor pathways. It controls skeletal muscles. The somatic nervous system is controlled by the motor cortex.
Autonomic system
The Autonomic Nervous System (ANS) is involuntary (i.e. not under conscious control). It ONLY has motor pathways and it controls smooth muscles and the internal organs and glands of the body. The ANS is controlled by the brain stem.
A) Sympathetic Nervous System (SNS): This is activated when a person is stressed. Heart rate and breathing increase, digestion stops, salivation reduces, pupils dilate, and the flow of blood is diverted from the surface on the skin (fight or flight response).
B) The Parasympathetic Nervous System (PNS): This is activated when the body is relaxing and so conserving energy. Heart rate and breathing reduce, digestion starts, salivation increases, and pupils constrict.
Neurons
Neurons are specialised nerve cells that move electrical impulses to and from the Central Nervous System (CNS).
Parts of a neuron
- Cell Body: Control centre of the neuron.
- Nucleus: Contains genetic material.
- Dendrites: Receives an electrical impulse (action potential) from other
neurons or sensory receptors (e.g. eyes, ears, tongue and skin). - Axon: A long fibre that carries the electrical impulse from the cell body
to the axon terminal. - Myelin Sheath: Insulating layer that protects the axon and speeds up
the transmission of the electrical impulse. - Schwann cells: Make up the myelin sheath.
- Nodes of Ranvier: Gaps in the myelin sheath. They speed up the
electrical impulse along the axon.
Sensory neuron
Sensory neurons are found in sensory receptors. They carry electrical impulses from the sensory receptors to the CNS (spinal cord and brain) via the Peripheral Nervous System (PNS). Sensory neurons convert information from sensory receptors into electrical impulses. When these impulses reach the brain they are converted into sensations, such as heat, pain etc. so that the body can react appropriately. Some sensory impulses terminate at the spinal cord. This allows reflexes to occur quickly without the delay of waiting for the brain to respond.
Motor neuron
Motor neurons are located in the CNS but project their axons outside of the CNS. They send electrical impulses via long axons to the glands and muscles so they can affect function. Glands and muscles are called effectors. When motor neurone are stimulated they release neurotransmitters that bind to the receptors on muscles to trigger a response, leading to movement
Relay neuron
Relay neurons are found in the CNS. They connect sensory neurons to motor neurons so that they can communicate with one another. During a reflex arc (e.g. you put your hand on a hot hob) the relay neurons in the spinal cord are involved in an analysis of the sensation and decide how to respond (e.g. to lift your hand) without waiting for the brain to process the pain.
Picture of neurons
Synaptic transmission
Neurons transmit electrical impulses between the presynaptic neuron and postsynaptic neuron. These electrical impulses, known as action potentials, reach the presynaptic terminal and triggers the release of neurotransmitters from sacks on the presynaptic membrane, known as vesicles. These neurotransmitters will then diffuse across the synaptic cleft, and then binds to a postsynaptic receptor site. This neurotransmitter is then taken back by the vesicles on the presynaptic neuron where they are stored for later release.
Excitatory and Inhibitory neurotransmitters
Excitatory neurotransmitters causes an electrical charge in the membrane of the post-synaptic neuron resulting in an excitatory post- synaptic potential (EPSP), meaning that the post-synaptic neuron is more likely to fire an impulse Inhibitory neurotransmitters cause an inhibitory post- synaptic potential (IPSP), making it less likely that the neuron will fire an impulse.
How is the likelihood that a neuron firing an impulse determined
A neuron can receive both EPSPs and IPSPs at the same time. The likelihood that the neuron will fire an impulse is determined by adding up the excitatory and the inhibitory synaptic input. The net result of this calculation, known as summation, determines whether or not the neuron will fire an impulse. If the net effect is inhibitory the neuron will not fire, and if the net effect is excitatory, the neuron will fire.
Direction of synaptic transmission
Information can only travel in ONE direction at a synapse. The vesicles containing neurotransmitters are ONLY present on the pre-synaptic membrane. The receptors for the neurotransmitters are ONLY present on the post-synaptic membrane. It is the binding of the neurotransmitter to the receptor which enables the information to be transmitted to the next neuron
Diffusion of the neurotransmitters mean they can only go from high to low concentration, so can only travel from the pre-synaptic membrane to the post- synaptic membrane.
Psychoactive drugs
Psychoactive drugs (medication that affects brain function to alter perception, mood or behaviour), such as SSRIs, work by affecting (increasing or inhibiting) the transmission of neurotransmitters across the synapse.
How does pain medication mimic the effects of inhibitory neurotransmitters
Stimulation of postsynaptic receptors by an inhibitory neurotransmitter results in inhibition of the postsynaptic membrane. When an inhibitory neurotransmitter binds to the post-synaptic receptors it makes the post- synaptic neuron less likely to fire. Due to summation, if inhibitory neurotransmitters are higher than excitatory neurotransmitters they can inhibit an action potential from occurring. Therefore, pain medications would decrease the overall activity and reducing brain activity may lead to less pain.
Endocrine system
The endocrine system provides a chemical system of communication in the body via the blood stream. Endocrine glands produce and secrete hormones into the bloodstream which are required to regulate many bodily functions. The major glands of the endocrine system include the pituitary gland and the adrenal glands. Each gland produces different hormones which regulate activity of organs/tissues in the body.
Pituitary gland
-The pituitary gland is located in the brain. It produces hormones whose primary function is to influence the release of other hormones from other glands in the body. The pituitary gland is controlled by the hypothalamus, a region of the brain just above the pituitary gland.
The hypothalamus receives information from many sources about the basic functions of the body. The hypothalamus then sends a signal to the pituitary gland in the form of a releasing hormone. This causes the pituitary gland to send a stimulating hormone into the bloodstream to tell the target gland to release its hormone. As levels of this hormone rise in the bloodstream the hypothalamus shuts down production of the releasing hormone and the pituitary gland shuts down secretion of the stimulating hormone.
Divisions of pituitary gland
1) The anterior pituitary gland releases the hormone called ACTH which
regulates levels of the hormone cortisol.
2) The posterior pituitary gland is responsible for releasing the hormone
oxytocin which is crucial for infant/mother bonding.
Adrenal cortex
The outer section of the adrenal gland is called the adrenal cortex. It produces the hormone cortisol which is produced in high amounts when someone is experiencing chronic (long-term) stress. Cortisol is also responsible for the cardiovascular system, for instance it will increase blood pressure and causes blood vessels to constrict.
Adrenal medulla
The inner section of the adrenal gland is called the adrenal medulla which produces adrenaline, the hormone that is needed for the fight or flight response that is activated when someone is acutely (suddenly) stressed. Adrenaline increases heart rate, dilates pupils and stops digestion.
Sympathomedullary pathway
The Sympathetic Nervous System (SNS) is triggered by the hypothalamus. The hypothalamus also sends a signal to the adrenal medulla (part of the adrenal glands), which responds by releasing a hormone called adrenaline into the bloodstream.
Adrenaline will increase heart rate, constrict blood vessels, increase rate of blood flow, raise blood pressure, divert blood away from the skin, kidneys and digestive system, increase blood supply to the brain and skeletal muscles, and increase respiration and sweating. All of this prepares the body for action and fight or flight by increasing blood supply, and therefore oxygen, to skeletal muscles for physical action and increasing oxygen to the brain for rapid response planning.
When the threat has passed the parasympathetic nervous system dampens down the stress response. It slows down the heartbeat and reduces blood pressure. Digestion, which is stopped when the SNS is active, restarts.
Evaluation of fight or flight response (2p, 3n)
+ The fight or flight response makes sense from an evolutionary psychology point of view because it would have helped an individual to survive by fighting or fleeing a threat.
+ Studies supports the claim that adrenaline is essential in preparing the body for stress. People who have malfunctioning adrenal glands do not have a normal fight or flight response to stress.
- Gray (1988) states that the first reaction to stress is not to fight or flight but freeze. This involves the person stopping, looking and listening and being hyper vigilant to danger.
- Taylor (2000) found that females tend and befriend in times of stress. Women have the hormone oxytocin, which means they are more likely to stay and protect their offspring.
- Von Dawans (2012) has found that even males also tend and befriend. For example, during the 2001 September 11th terrorist attacks both males and females showed tend and befriend as they tried to contact loved ones and help one another.
Localisation of function
Localisation of function refers to the principle that functions (e.g. vision, hearing, memory, etc.) have specific locations within the brain. Research has shown that some functions are more localised than others. The motor and somatosensory functions are highly localised to particular areas of the cortex. Other functions are more widely distributed. The language system uses several parts of the brain, although some components, such as speech production, may be localised (Broca’s Area).