Key Terms Flashcards
(20 cards)
What is the central nervous system? (CNS)
The brain and spinal cord. These control the flow of messages & information from our senses. The CNS compromises billions of neurones which pass information around the CNS using neurotransmitters.
What are neurones and what do they do?
Special nerve cells that convey messages around the body. Within a neurone, the message is an electro-chemical one called a nerve impulse. However, there are tiny gaps between neurones (called synapses) where purely chemical messages are passed between neurones. Although neurones only release a limited number of neurotransmitters they can receive & respond to many more. (There are estimated to be more than 100billion neurones in the human nervous system).
What are neurotransmitters?
These are the chemical messengers released through the synapses; they are released from the end of one neuron (terminal button/pre-synaptic terminal), cross the gap between neurones called the synaptic gap/cleft & attach themselves to the post-synaptic receptor sites on the next neuron. When there are enough neurotransmitters attached to the post- synaptic receptor sites a nerve impulse is created & a message sent along the neuron: the neuron ‘fires’ & an action potential is created, if no message is sent & the neuron remains ‘dormant’ that is referred to as a resting potential.
What does it mean if neurotransmitters are inhibitory or exciting?
Neurotransmitters can also be inhibitory or excitatory. Dopamine is an excitatory neurotransmitter, it encourages neurones to fire sending more information/sensations; GABA is an inhibitory neurotransmitter (which is released when we drink alcohol) & prevents messages from being sent between neurones; this explains why when we drink we might suffer loss of memory, balance, inhibitions etc. as the neurones conveying this information do not fire.
What types of neurotransmitters are there?
Neurotransmitters include: dopamine (linked to reward/pleasure & movement); serotonin (mood); endorphins (physical & psychological suppression of pain).
What are hormones and what do they do?
Like neurotransmitters, hormones are chemical messengers. They are secreted by glands: glands & hormones form the endocrine system. Hormones foster the growth & proliferation of cells. Hormones work by attaching themselves to receptor cells on the surfaces of target organs, or by entering the target cells of target organs directly; e.g., sex hormones, oestrogen (ovaries) & testosterone (testes), are released by the gonads (sex organs) & are responsible for many of the developmental changes that occur around puberty. These changes are specific to certain parts of the body because these are the target organs, e.g., breasts in women, or facial hair follicles in men. The changes induced by hormones can have psychological aswell as physical effects. The nature of the effect of the hormone, as with neurotransmitters, depends on the characteristics of the receptor cells that receive the hormones/neurotransmitters; e.g., the same hormones that speed up heart rate can slow the digestive system (adrenalin & noradernalin). However, hormones differ significantly from neurotransmitters: the effects of hormones tend to be far longer lasting, e.g., sex hormones & puberty; and hormones can affect target organs in different part of the body, neurotransmitters affect the adjacentneuroneonly. Unlike NTs, hormones take longer to work & tend to be used to effect longer-term changes.
What are synapses?
These are the small junctions between neurones where neurotransmitters are released & passed from the terminal button of one neurone (pre-synaptic membrane) to the dendrite of the receiving neurone (receptor site on post-synaptic membrane). One neurone can make up to a 1000 connections with adjacent neurones. Synapses can be inhibitory or excitatory: inhibitory=prevent neurone from firing; excitatory=causes the neurone to fire. When a neurone ‘fires’ it transmits a message, e.g., pain.
What are genes and what do they do?
The messages (or units of information) that we inherit from our parents that control aspects of our development. Genes are physical particles that determine some aspect of development/inheritance; dominant genes exert a noticeable effects, even in a person who has only 1 copy per cell; recessive genes require 2 copies per cell for the influence to be expressed. Genotype=the particular set of genes carried; phenotype=the expression of the genotype. Genes are made up of DNA (deoxyribonucleic acid) which is responsible for the protein synthesis which influences our development. They are contained on chromosomes which are found within the nuclei of cells; we inherit 23 chromosome from each parent, which is thought to account for shared behavioural & physical traits between family members. Genes control physical processes in the body & some control specific behaviours/traits (e.g., eye colour, being able to roll your tongue). However, it is rare for a single gene to control a specific behaviour/trait. More typically genes interact with one another to influence behaviour & traits. Genes may also interact with environmental factors to determine & shape behaviour/traits. We share a lot of the same genetic make-up, which explains similarities between within families etc., but there are also differences in our genetic make-up which can account for differences in our behaviour/traits.
What is a neuron?
A cell within the CNS.
What is the cell body/ soma?
Contains the nucleus, which houses the genetic material for that particular neuron. It also contains other materials that allow the cell to function, e.g., mitochondria, where aerobic respiration occurs, where energy is released from glucose, which provides the neurone with energy.
What are dendrites?
Attached to the cell body, they receive information from other neurons in order to trigger an action potential- an electrical impulse- within the cell.
What is an axon?
Also attached to the cell body, an extension of the cell body that passes the electrical impulse towards the axon terminals.
What are the nodes of ranvier?
There are gaps between the Schwann cells that make up the myelin sheath called nodes of (X)Ranvier, that are uninsulated sections of the axon, therefore, capable of generating electrical activity, effectively acting as repeater stations, boosting the electrical impulse.
What are axon terminals?
Located at the very end of the axon, on the ends of the axon terminals are terminal buttons. Nerve impulses are passed to another neuron, or to a muscle or gland etc. The axon terminals are bulb-shaped structures that contain tiny sacs called vesicles; vesicles store neurotransmitters.
What is the action potential?
The electrical trigger/impulse that passes along the axon & stimulates the neuron to activate & release neurotransmitters as a result of synaptic transmission. Created by DEPOLARISATION.
What is a resting membrane potential?
The difference in electrical potential–how ‘ready’ the neuron is for ‘action’/ firing– on each side of the cell membrane while the neuron/nerve cell is at rest. Returning to a POLARISED STATE
What are electrostatic forces (electrical gradient)?
Opposites attract, positive ions are attracted to the negative ions & vice versa. Is affected by the concentration gradient.
What is depolarisation?
Depolarisation occurs when sodium (Na+) ions enter the membrane quicker than the sodium-potassium pump can remove them. At this point, the selectively permeable walls of the membrane open up & even more Na+ can enter the membrane; Na+ enters quicker than potassium (K+) exists (N.B., Ka+ is positively charged), making the inside of the membrane even more positively charged.
What is the axon hillock?
At the top of the axon, attaching the axon to the cell body is the axon hillock, which is where the nerve impulse is triggered from.
What is the myelin sheath?
Around the outside of the axon are layers of fatty deposits called a myelin sheath, that acts as insulation for the electrical impulse that travels along the axon & speeds up the rate of message transmission (damage to the myelin sheath is linked to Parkinson’s Disease, where messages are not relayed properly).
