The Brain and Nervous System Flashcards
Why is nervous system needed
- communication between organisms
- controls functions of the organism
- regulates responses
Neurons
- never cells capable of producing and transmitting electrical impulses
Anatomy of a neuron
- Soma
- Dentrites
- Axon
Soma
- neuronal cell body
- contains nucleus
- site of protein synthesis
Dendrites
- many per neuron
- receive incoming inputs from other neurons
- converge on the soma
Axon
- single axon carries impulse to next neuron in series
- axon terminal branches into many terminal boutons
- insulated with fatty coating termed the myelin sheath
Synapses
connection between neurons
how many neurons in human brain
100 billion
What does neurotransmitter removal ensure
that nervous system signalling is rapid and dynamic
how many mechanisms - removal of neurotransmitter from synapse
3
- removal of neurotransmitter
neurotransmitters can be returned to axon terminals for reuse or transported into glial cells
- removal of neurotransmitter
enzymes inactivate them
- removal of neurotransmitters
can diffuse out of the synaptic cleft
Divergence of signal
synapse expands signals throughout the nervous system
Convergence of signal
synapse expand signals specifically down a certain nerve tract
Afferent neurons (incoming neurons)
- carry information from periphery into nervous system
- convert sensory info into action potential
= use specialised receptors to do this
Efferent neurons
- carry commands from nervous system to effectors
- glands, muscles
Interneurons
- form connections and circuits between neurons
- connect afferent - efferent
- increase complexity of NS
-involved in storing info
What is withdrawal reflex
- simplest form
- involves 1 afferent, 1 efferent and 1 interneuron
-only requires impulse through spinal cord - facilitates rapid response, termed spinal reflex
Nerve net
- neural network
- simple
- small numbers of connected neurons
Nervous system
- complex
- Hughe numbers of cells connected
- often contains many sub-divisions and components
Ganglia
paired or grouped neurons
ganglion
singular neuron
Function of glial cells
- support and hold neuron in place
- supply nutrients/O2
- insulate neurons electrically
- protect from pathogens
What are glial cells
cell that support neurons
Types of glial cells
- Astrocytes (CNS)
- Schwann cells (PNS)
- Oligodendrocytes (CNS)
- Microglia
Astrocytes (CNS)
- star shaped
- BBB
- protects brain from toxins in blood
- role in inflammatory response in brain
- control and coordinate the glial cells
The Blood Brain Barrier
- made up of cell membranes
- permeable to fat soluble substances
Schwann cells (PNS)
- rich in lipid and produce myelin
- wrap around axons (myelin sheath)
- gives white appearance
- myelin provides electrical insulation
- enhances speed
- saltatory conduction
Oligodendrocytes (CNS)
- myelin producing cell in CNS
- highly branched
- single ODC produces myelin for several axons
What is Multiple Sclerosis
disease of the myelin - immune system destroys the sheath
Symptoms of multiple sclerosis
- pins and needles
- loss of motor function
- visual disturbance
Central nervous system
- myelinating cell = oligodendrocyte
= single oligodendrocyte to many axons
Peripheral nervous system
- myelinating cell = Schwann cell
= single axon to many Schwann cells
Microglia
- small, immune cells
- act as phagocytes
- primary immune defence in CNS
- work closely with astrocytes to protect neurons
Why is microglia so important
as few antibiotics cross the BBB
How can the PNS have the capacity to repair itself
contains few specialised support cells
- glial cells promote axon growth
why can’t the CNS repair itself
Glial cells form a physical and chemical barrier to prevent regrowth
Brain stem
controls basic, autonomic functions
Cerebellum
integrates sensory and motor movements (precision)
Cerebrum
complex behaviour, emotions, learning, memory
Hindbrain
Cerebellum, pons and medulla
Ponds and medulla
- connects spinal cord and brain
- control involuntary functions - breathing
= hindbrain
Midbrain
- sensory inputs
- mainly vision and olfaction
Telencephalon
cerebrum
- 2 hemispheres
- complex array of lobes
- perception, learning, memory, conscious behaviour
The forebrain
Telencephalon, Diencephalon
Diencephalon
Thalmus, Hypothalamus
Thymus
final sensory relay between spinal cord and forebrain
Hypothalamus
regulates many function like temperature, thirst, hunger
The corpus callosum
divides the two hemispheres and allows communication between the two
What is the outer region of the cerebral hemisphere
cerebral cortex
what is the cerebral cortex
grey matter
- forms layer over brain surface
What are the ridges called in brain tissue
gyri
What are the valleys called in Brian tissue
sulci
Brain and spinal cord are divided into what two matters
white and grey matters
what is grey matter in the cerebral hemisphere
mainly neuronal cell bodies
what is white matter in the cerebral hemisphere
mainly axons
- myelin gives white appearance
The lobes of the cerebrum
Temporal
Frontal
Parietal
Occipital
Anatomy of lobes of the cerebrum
Boxing glove
Thumb - temporal
Curled fingers - frontal
Back of had - parietal
Wrist - occipital
contralateral control
right hemisphere controls left side of the body
left hemisphere controls right side of the body
Temporal lobe
- role in auditory processing
- recognition and naming objects/ faces
What is it called when the temporal lobs is damaged
agnosia
agnosia
aware of objects but can’t name them
Frontal lobe
stimulation of specific areas
- specific muscles contract
what separates frontal lobe from parietal lobe
central sulcus
other functions of frontal lobe
personality
planning
social conscience
awareness
What is the primary motor cortex
strip of frontal cortex in front of central sulcus
Who was Phineas gage
- construction worker in 1848
- survived explosion = rod through his frontal
= became unrecognisable
Parietal lobe
stimulation of specific areas
- touch, lips, fingers, gentiles
primary somatosensory cortex
strip of parietal cortex behind central sulcus
somatosensory
relates to sensory inputs
Motor
relates to movement of body parts
What does disproportionate representation relate to
Degree of fine motor control
Degree of touch sensitivity
Contralateral neglect syndrome
damage to right parietal lobe
Contralateral neglect syndrome
damage to right parietal lobe
What does PET scanning stand for
Positron Emission Tomography
What is PET scanning
Radioactive substance injected and detected as it passes through the brain
= allows detection of active areas in the brain
Language processing - speaking a written word
- words detected by visual cortex
- processed - Wernickes area
- transmitted to Brocas area
- Brocas area stimulates motor cortex to speak word
Language processing - speaking a heard word
- words detected by auditory cortex
- processed by Wernicke area
- transmitted to brocas area
- brocas area stimulates motor cortex to speak word
