Chapter 3 Flashcards
Neuron
- nerve cell specialized for communication
Draw a labelled diagram of a neuron
.
Dendrite
- projection that picks up impulses from other neurons
- portion of neuron that receives signals
Axon
- nerve fibre projecting from the cell body that carries nerve impulses
- portion of the neuron that sends signals
Synaptic vesicles
- spherical sac containing neurotransmitters
- travel the length of the axon to the axon terminal
- it bursts to release neurotransmitters when it reaches the end of the axon terminal
Node
- gap in the myelin sheath of an axon which helps the conduction of nerve impulses
Myelin sheath
- fatty coat that insulates the axons of some nerve cells, speeding transmission of impulses
- glial cells wrapped around axons that act as insulators of the neuron’s signal
Cell body
- materials needed by the neuron are made here
- aka soma
Neurotransmitters
- chemical messenger specialized for communication from neuron to neuron
Synapse
- terminal point of axon branch which releases neurotransmitters
- space between two connecting neurons through which messages are transmitted chemically
- consists of a synaptic cleft
Synaptic cleft
- a gap into which neurotransmitters are released from the axon terminal
- gap is surrounded by small patches of membrane on each side (one of the sending axon and one on the receiving dendrite)
Glial cell
- cell in nervous system that plays a role in the formation of myelin and the blood-brain barrier, responds to injury, removes debris, and enhances learning and memory
Astrocytes
- type of glial cell that communicate closely with neurons, control blood flow in the brain, and play a vital role in the development of the embryo
- abundant in the blood-brain barrier (protective shield that insulates the brain from infection by bacteria and other intruders)
Oligodendrocyte
- make up the myelin sheath
Resting potential
- electrical charge difference (-60mV to -70mV) across the neuronal membrane, when the neuron is not being stimulated or inhibited (inside more negative than outside)
Threshold
- membrane potential necessary to trigger an action potential
- differs between neurons, but in many it is -55mV
Action potential
- electrical impulse that travels down the axon, triggering the release of neurotransmitters
Absolute refractory period
- time during which another action potential is impossible; limits maximal firing rates
Graded potentials
- postsynaptic potentials that can be excitatory or inhibitory depending on whether positively or negatively charged particles flow across the neuronal membrane and in which direction they flow
EPSP
- excitatory postsynaptic potential
- graded potential in a dendrite that is caused by excitatory synaptic transmission
IPSP
- inhibitory postsynaptic potential
- graded potential in a dendrite that is caused by inhibitory synaptic transmission
Receptor site
- location that uniquely recognizes a neurotransmitter
Reuptake
- means of recycling neurotransmitters
- a process by which the synaptic vesicle reabsorbs the neurotransmitter
List the steps for an action potential to occur
- Resting state
- Depolarization
- Rising phase of the action potential
- Falling phase of the action potential
- Undershoot
Step 1: Resting State
-60mV to -70mV
nothing is happening
potassium ions concentrated inside
Step 2: Depolarization
More positive charged ions enter Sodium channels open Sodium ions come into the cell Cell is less polar (ie. less charged) Once potential reaches -50mV, it hits the threshold and cell will “fire”
Step 3: Rising Phase
Reaches ~ +50mV
Potassium channels are closed, but sodium is rushing in causing this increase in charge potential
Step 4: Falling Phase
Sodium channel closes and potassium channels opens
The potassium ions move out because of charge concentration gradient AND because of concentration gradient
The potential is therefore dropping (positive potassium ions are leaving)
Step 5: Undershoot
Refractory period, membrane is hyperpolarized
More polarized (more negative) than resting potential
Much more difficult for cell to fire again
Short pause where the cell is too negative to get back to threshold; can’t fire
List 8 major neurotransmitters
- Glutamate
- GABA
- Acetylcholine
- Norepinephrine
- Dopamine
- Serotonin
- Endorphins
- Anandamide
Glutamate
Main excitatory neurotransmitter in the central nervous system; participates in relay of sensory information and learning
GABA
Main inhibitory neurotransmitter in the central nervous system
Acetylcholine
Muscle contraction
Cortical arousal
Norepinephrine
Brain arousal and other functions like mood, hunger, and sleep
Dopamine
Motor function and reward
Serotonin
Mood and temperature regulation, aggression, and sleep cycles
Endorphins
Pain reduction
Anandamide
Pain reduction, increase in appetite
Monoamines
- contain only one amino acid
- includes norepinephrine, dopamine and serotonin
How does the myelin sheath work?
- Help speed up transmission of the action potential
- Positive charge has to travel all the way down the axon
- Myelin sheath made by glial cells wrap around the axon, prevent potassium/sodium from exiting
- The action potential jumps between the gaps (nodes of ranvier)
- Signal stays stronger and is transmitted faster
Neural plasticity
- ability of the nervous system to change
Neural plasticity over development
- Growth of dendrites and axons
- Synaptogenesis, the formation of new synapses
- Pruning, consisting of the death of certain neurons and the retraction of axons to remove connections that aren’t useful
- Myelination, the insulation of axons with a myelin sheath
Neural plasticity and learning
- brains change as we learn
- formation of new synapses
- generating increased connections/communication among neurons
- strengthening of existing synaptic connections, so that the neurotransmitters released into synapses produce a stronger and more prolonged response from neighbouring neurons (potentiation; long-term potentiation)
Neural plasticity following injury/degeneration
- adult neurogenesis: creation of new neurons in the adult brain
- stem cells: use of undifferentiated cells to replace damaged neurons
Structural plasticity
- change in the shape of neurons
- may be critical for learning
- more elaborate dendrites, expansion of relevant brain areas
Central nervous system
- part of the nervous system containing the brain and spinal cord that controls the mind and behaviour
Peripheral nervous system
- nerves in the body that extend outside the central nervous system
- consists of the autonomic and somatic nervous system
Somatic nervous system
- interacts with external environment
- controls voluntary behaviour
- afferent nerves carry sensory signals from sense receptors to the CNS
- efferent nerves carry motor signals from the CNS to the skeletal muscles
Autonomic nervous system
- regulates internal environment
- controls involuntary functions
- afferent nerves carry sensory signals from the internal organs to the CNS
- efferent nerves carry motor signals from the CNS to the organs
- consists of sympathetic (fight/flight) and parasympathetic (rest/digest)
Spinal cord
- part of the central nervous system
- connects the brain to the rest of the body
- acts as a medium for communication
- contains interneurons
Reflexes
- connect sensory neurons directly to motor neurons via the interneuron in the spinal cord
- forms a reflex arc
- allows for actions to be completed much faster than they normally would if the information travelled up to the brain to be processed before going to the motor neurons
- adaptive trait that helps our survival
Forebrain
- allows for human nature, thinking, panning, advanced intellectual abilities
- consists of the cerebral cortex and subcortical structures
Cerebral cortex
- 2 hemispheres separated by the corpus callosum
- gyrus = smooth raised surfaces, sulcus = indentations/fissures
- consists of occipital, temporal, parietal, frontal lobes
Occipital lobe
- processes visual information
Temporal lobe
- processes auditory information
- contains primary auditory cortex
- Wernicke’s area: processing language
Parietal lobe
- processes information from touch
- somatosensory cortex: different folds of brain related to different body parts
Frontal lobe
- abstract thinking, language, memory, judgement, movement
- motor cortex
- Broca’s area: regulates/produces speech
Broca’s area
- located in frontal lobe
- helps to control speech production
Wernicke’s area
- located in the temporal lobe
- involved in understanding speech
Subcortical structures
- pituitary gland
- basal ganglia
- limbic system
Pituitary gland
- master gland that releases hormones that regulate and influence other glands and organs
- controlled by the hypothalamus
Basal ganglia
- responsible for direct, intentional movement; control posture
Limbic system (components + description)
- emotional centre of the brain; the 4 f’s (feeding, fighting, fleeing, sex)
- thalamus: receives and filters information from the senses to be sent to the cortex
- hypothalamus: body temperature, thirst, sexual behaviour
- hippocampus: creates new memories, sends them to the cerebral cortex for storage
- amygdala: central role in emotion, creating emotional memories involving fear
Midbrain
- part of the brain stem that contributes to movement, tracking of visual stimuli, and reflexes triggered by sound
- consists of two regions: tectum and tegmentum
- tectum orients the organism in its environment to visual (superior colliculi) and auditory (inferior colliculi) stimuli
- tegmentum is involved with movement and arousal; also helps orient the organism toward sensory stimuli
Hindbrain
- region below the midbrain that contains the cerebellum, reticular formation, pons, and medulla
- an area of the brain that coordinates information coming into and out of the spinal cord
Contralateral control
- each side of the brain controls the opposite side of the body
Split brain patients
- split brain patients have lack of communication between the two hemispheres due to the removal of the corpus callosum
- disruption between the two sides, causing linked characteristics such as speech corresponding to bodily movement to become disjointed
Hormone
- chemical released into the bloodstream that influences particular organs and glands
- they’re carried through our blood vessels unlike neurotransmitters (carried through nerves)
- slower in their actions than neurotransmitters
- outlast neurotransmitters in their effects; slower but more enduring
List the major hormones
- oxytocin
- adrenalin
- cortisol
- sex hormones (testosterone/estrogen)
Oxytocin
- trust, reproductive functions
Adrenalin
- increases during stressful situations, heightens physical ability
Cortisol
- increases during stress, regulates blood pressure, cardiovascular function, bodily use of fats, proteins, carbohydrates
Testosterone/Estrogen
- sex hormones
- testosterone increases sex drive in males
Corpus callosum
- large band of fibres connecting the two cerebral hemispheres
Medulla
- an extension of the spinal cord that coordinates heart rate, circulation and respiration
Reticular formation
- responsible for regulation of sleep, wakefulness and arousal
Cerebellum
- largest structure of the hindbrain and controls fine motor skills
Pons
- structure that relays information from the cerebellum to the rest of the brain
Endocrine system
- system of glands and hormones that controls secretion of blood-borne chemical messengers
EEG
- electroencephalograph
- a device to measure brain’s electrical activity, using data from placing electrodes on multiple spots on the brain
PET
- positron emission tomography
- uses radioactive glucose and a scanner to track where the radioactivity is located
- brain uses glucose when it is active
CT scan
- computed tomography
- 3D reconstruction of multiple x-rays
MRI
- shows structural detail
- magnetic resonance imaging
- measures the release of energy from hydrogen atoms in biological tissues following exposure to a magnetic field
- good at detecting soft-tissues, such as brain tumours (unlike CT scan)
fMRI
- functional magnetic resonance imaging
- measures change in blood oxygen level
TMS
- transcranial magnetic stimulation
- applies strong/quickly changing magnetic fields to the skull to create electrical fields in the brain
- interrupt/enhance brain function in a specific region
- can be used to see how TMS affects functioning; can infer causation
MEG
- magnetoencephalography
- detects electrical activity in the brain by measuring tiny magnetic fields
- reveals patterns of magnetic fields on the skull’s surface
- strength is in its ability to track brain changes over milliseconds rather than second (like PET and fMRI)
Lateralization
- cognitive function that relies more on one side of the brain than the other
Left hemisphere
fine-tuned language skills, making facial expressions, motion detection, speech comprehension/production
Right hemisphere
coarse language skills, perceptual grouping, face perception
Antagonist
- a drug/ligand that blocks or dampens a biological response by binding to and blocking a receptor rather than activating it like an agonist
Agonist
- a drug/chemical that binds to a receptor and activates the receptor to produce a biological response
- causes an action
