module 2 Flashcards
what are the 3 major parts of the brain
cerebrum
cerebellum
brainstem
cerebrum
two hemispheres divided by the longitudinal fissure
cerebral cortex
the outermost surface layer of the cerebrum (grey matter)
contains the cell bodies of the brain neurons
frontal lobe
executive functions:
- reasoning, planning, problem-solving
- inhibitory control
- working memory
motor functions:
- premotor cortex - motor planning
- primary motor cortex - execution
speech production (Broca’ area)
parietal lobe
primary somatosensory cortex:
- perception of touch
sense of space and locations
spatial attention:
- directing attention and eye-movements to explore visual world
linking vision to action:
- represents spatial location of objects around us for guiding actions
occipital lobe
Posterior part of the brain, inferior to parietal lobe
primary visual cortex (V1):
- all visual perception
Higher visual area:
- different regions process shape, colour, orientation, motion
temporal lobe
primary auditory cortex:
- perception of sound
Language comprehension:
- (Wernicke’s area)
medial temporal lobe:
- limbic system
(amygdala and hippocampus)
limbic system medial temporal lobe
amygdala:
- fear and arousal
- responds to threat/danger (snakes. spiders, angry/fearful faces)
- fear
Hippocampus
- learning and memory
- forming new episodic memories
- damage causes anterograde amnesia
corpus callosum
- neuron connections between the left and right hemispheres
- allows brain communication between hemispheres
- split brain patients - left and right hemispheres disconnected. The two hemispheres cannot communicate with each other
Phineas gage
- railway worker, Phineas Gage, accident in 1848
- iron rod, about 1. length, went through his head
- remained conscious during and after accident
- damaged frontal lobes
- died 12 years later and his skull was examined
Broca’s area - speech production
in 1861, Paul Broca described a patient who was unable to speak after damage to the left frontal lobe (Broca’s area)
- speech is slow and non-fluent
- difficulty finding appropriate words (anomia)
- speech still carries meaning
- comprehension is (mostly unaffected)
Wernicke’s area - language comprehension
in 2874, Carl Wernicke suggested that lesions to the left posterior temporal lobe led to deficits in language comprehension
- unable to understand language - deficit in comprehension
- speech is fluent with normal prosody
- speech has no meaning, nonsense, speech
Wilder Penfield
- stimulated the brain with electrical probes while the patients were conscious, during surgery for epilepsy
- in 1951, published maps of motor and sensory cortices of the human brain
homunculus
- primary sensory cortex and primary motor cortex
- brain function “mapped” by electrical stimulation
- brain stimulation leads to sensation or movement (muscle twitch)
size of area on cortex determines sensitivity or fine motor control
central nervous system
brain and spinal cord
peripheral nervous system
somatic nervous system (voluntary, motor and sensory)
autonomic
(involuntary, heart rate, respiration, sweating, stress, arousal, “fight or flight”)
Autonomic nervous system’s two divisions
sympathetic and parasympathetic
sympathetic nervous system
- emotional arousal, stress, fear
- fight or flight response
- increases heart-rate, respiration. perspiration. pupils dilate
parasympathetic nervous system
- rest and digest
- lowers heart-rate, respiration
- increases stomach, intestine activity (digestion)
- opposes the sympathetic nervous
brainstem
medulla
- autonomic nervous system functions
- controls heart rate, respiration, regulation of blood pressure, body temperature
- reflex centres for coughing, sneezing, swallowing, vomiting
disorders of consciousness
- severe damage to upper brain (hemispheres and cortex)
- of brainstem is not damaged, autonomic nervous system functions can remain
- sometimes normal respiration, control of heart rate, some face and eye movement remain
locked in syndrome
- amyotrophic lateral sclerosis (ALS) or motor neurons disease
- loss of motor neurons to spinal or brain injury
- intact cerebrum and brainstem, but disconnected from spinal cord
- normal cognitive function, vision, and hearing, but patients cannot move
- patients may be fully conscious and aware, but totally unresponsive
medulla
- Autonomic nervous system
- Controls heart-rate, respiration, regulation of blood pressure, body temperature
Reflect centres for coughing, sneezing, swallowing, vomiting
- Controls heart-rate, respiration, regulation of blood pressure, body temperature
persistent vegetative state
- sever damage to upper brain
- if brainstem is not damaged, autonomic nervous system functions can remain
- sometimes normal respiration, control of heart rate, some fave and eye movements remain
cerebellum
- hind brain
- sense of balance and co-ordination
- motor learning
dendrite
- unique to neurons
- received signals
axon
- sends signals
- wrapped in myelin for efficient transmission of signals along the axon
axon terminals
- form synapses with other neurons
- secrete neurotransmitters to send signals across synapses to other neurons
glial cells
supporting cells for neurons
three types of glial cells
oligodendrocytes, astrocytes and microglia
oliogodendrocrytes
produce the myelin sheath that wraps around axons
astrocytes
supply nutrients from blood to the neurons.
main blood-brain barrier
microgolia
brain’s immune system. clean up foreign or toxic substances
the myelin of axons
oligodendrocytes form myelin sheath by wrapping around the axon. essential for efficient communication, for propagation of signals along axon.
multiple sclerosis
involves loss of myelin, disruption of efficient neural communication throughout the body
synapses
join axon terminals of one neuron for transmission of signals between neurons
pre-synaptic
before the synapse. from cell body to axon terminal
post synaptic
after the synapse. from dendrite to cell body
sodium and potassium are…
positively charged ions
membrane potential
difference in the electrical charge (voltage) between inside and outside cell, across cell membrane wall
resting potential
at rest. more positive ions outside than inside the cell gives overall negative potential inside compared with outside the cell
what is the different in electrical charge at rest
-70mV
ion channels
in cell membrane wall open and close to pass or block movement of ions across cell membrane
three types of ion channels
sodium potassium pump
voltage dependent ion channels
ligand-gated ion channels
ion channel 1: sodium potassium pump
- Actively pumps Na+ and K+ across cell membrane
- Overall pumps positive charge out of cell (3 Na+ out for every 2 K+ in)
Use energy - about 25% of body total energy, 70% of brain energy!
- Overall pumps positive charge out of cell (3 Na+ out for every 2 K+ in)
action potential
Transmission of electrical signal along axon
depolarisation of cell:
membrane potential goes back to 0
repolorisation
membrane potential back to -70mV resting potential
ion channel 2
voltage-dependent ion channels
- Voltage-depended ion channel, closed at resting potential
- Open when membrane potential reaches threshold voltage
- Allows flow of ions across cell membrane
synapses
join axon terminals of one neuron to dendrites of another neuron for transmission of signals
re-takeup pump
clears neurotransmitter from synaptic cleft back into pre-synaptic terminal
enzymes
break down neurotransmitter in synaptic cleft
parkinsons disease
loss of dopamine in the basal ganglia deep in the brain
reflex
Sensory neuron (input) passes signal to motor neuron (output) to cause muscle contraction.
Sending signals: neurotransmitter release
- Depolarisation of axon terminal (action potential) triggers release of neurotransmitter
- Neurotransmitter acts on receptor on post-synaptic neuron to open ion channels and pass signal
ligand gated ion channels
- Neurotransmitter receptors open ion channels when neurotransmitter binds
- Different neurotransmitters bind to and open different ion channels (Na+, K+, CI-) to change membrane potential in different ways
receptor binding
- Can cause depolarisation (less negative) e.g. Na+ flow in
Can cause hyperpolarisation (more negative) e.g. K+ flows out or CI= flows in
excitatory
- Receptor opens channels that cause depolarisation
- ESPS: excitatory post-synaptic potential
Closer to threshold for action potential
- ESPS: excitatory post-synaptic potential
inhibitory
- Receptor opens channels that cause hyperpolarisation
- IPSP: inhibitory post-synaptic potential
- Further from threshold for action potential
graded potentials
- Excitatory and inhibitory inputs (via dendrites) combine together
- Change membrane potential on postsynaptic cell
- Graded potential on postsynaptic cell depends on strength of synapse connection (on dendrite)
neural integration
Determines whether sensory neuron (input) passes signal to motor neuron (output) to cause muscle contraction
eeg, erp, mri and fmri
EEG: electroencephalography
ERPs: event-related potentials
MRI: magnetic resonance imaging
fMRI: functional magnetic resonance imaging
Single neuron recording
- Place a thin electrode into an animal’s brain (rat, cat, monkey)
- Record action potentials “firing” from a single neuron
Measure what that neuron encodes or detects
- Record action potentials “firing” from a single neuron
EEG-electroencephalography
- Summed activity from action potentials of neurons in the cortex cause electrical activity change on the scalp (skin of the head)
Measure voltage changes from electrodes placed in the scalp
used for detecting sleep and seizures
erp
detecting deafness of baby
ERPs can show precise time of information processing in the brain
- 100ms viewing any stimuli
- Peak of brain activity 100ms after seeing visual stimulus
170ms viewing face
Problems of ERP
- Difficult to accurately localise activity to specific brain areas
- Poor spatial resolution
- Measures electrical potential conducted across the scalp
Hard to determine exactly where in the brain this activity comes from
fMRI
- Measures change in blood oxygen level
- Active neurons use oxygen
change in blood oxygen levels = change in brain activity
- Active neurons use oxygen
problems with fMRI
- Indirect measure of brain activity
- BOLD signal from change in blood oxygen level
- Not precise timing of neural activity
- Very expensive
