NS- organisation and brain anatomy Flashcards
What is grey matter, where is it found
all unmyelinated parts of neuron (unmyelinated axons, cell bodies, dendrites, axon terminals) and neuroglia
only found
- at periphery of brain
- A few clusters deep within brain
- innermost layer of spinal cord
- called nuclei in CNS and ganglia in PNS (with exception of basal ganglia which is situated in cerebrum)
what is white matter
composed of myelinated axons and dendrites
- CNS- majority of brain tissue and periphery of spinal cord
- PNS- most neuron axons
What are sensory / afferant nerves
carry info from body to spinal cord
impulses may then pass to the brain, or to connector neurones of reflx arcs in the spinal cord
what are sensory receptors
specialised endings of sensory neurones
respond to different stimuli inside / outside the body
what are somatic, cutaneous or common senses
sense that originate from the skin
pain, touch, heat and cold
sensory nerve endings in the skin transmit action potential to the brain where sensation is perceived
what are proprioceptor senses?
senses originating in muscles / joints
send info to the brain about the position of the body and its parts in space
enables maintenance of posture and balance
what are autonomic afferent nerves
originate in internal organs, glands and tissues
what are motor / efferent nerves?
motor nerves originate in the brain, spinal cord and autonomic ganglia
motor nerves transmit impulses to the effector organs (muscles and glands)
2 types
- somatic nerves (voluntary and reflex skeletal muscle contraction)
- autonomic nerves (involuntary)- involved in cardiac + smooth muscle contraction and glandular secretion
- sympathetic
- parasympathetic
describe the nerve pathway for somatic nerves
“lower motor meurone”- only one neurone that leaves spinal cord and travels directly to the skeletal muscle
Synapse is called Neuromuscular junction, NT is always acethycholine
describe nerve pathway for autonomic nerve pathways
involve two nerves
- preganglionic neurone leaves spinal cord and synapses with a second nerve (postganglionic neuron)
- postganglionic neurone synapses with the effector tissue (cardiac muscle / smooth muscle / glands)
main NT’s are noradrenaline (norepinephrine) and acetycholine
- postganglionic neurone synapses with the effector tissue (cardiac muscle / smooth muscle / glands)
what are mixed nerves
nerves found outside the spinal cord
the sensory and motor nerves are enclosed within same sheath of connective tissue (rather than being arranged in separate groups (Tracts) as they are in hte spinal cord
what are the 4 types of neuroglia
astrocytes-
- most abundant
- allow nutrient exchange between neurons and blood vessels
- form part of the blood-brain barrier (selective barrier that protects brain from potentially toxic substances and chemical variations in the blood)
oligodendrocytes
- produce myelin (in CNS)
- Myelin insulates neurons and increases conduction speed
ependymal cells
- line cavities in the brain and spinal cord
- produce adn circulate CSF
microglia
- monitor health of neurons
- remove dead / injured neurons
what are properties of neurones
cell body + axon + dendrites
cannot divide
need continuous supply of oxygen + glucose for survival
can normally synthesize ATP from glucose only (unlike many other cells)
Differentiate betwen function of neurons and neuroglia
neurons - transmit electrical impulses
neuroglia- protect, nurture neurons (e.g. produce myelin to increase conduction speed, remove dead + injured cells, allow nutrient exchange between neurons and blood vessels whilst maintaining blood brain barrier), produce CSF
name the lobes and principal suci of the brain
frontal cortex
parietal lobe
occipital lobe
temporal lobe
Outline the position and functions of thalamus and hypothalamus
Diencephalon- connects cerebrum and Midbrain
consists mainly of
- Thalamus
- relay station for sensory impulses from spinal cord, brain stem and cerebellum (incl. sensory receptors in skin and viscera)
- incoming info is “sorted” and “Edited” before being relayed to appropriate cerbral cortices for interpretation
- involved in recognition, arousal, processing some emotions and complex reflexes
- Hypothalamus
- located below and in front of the thalamus, immediately above pituitary
- both nervous and endocrine organ
- controls output of hormones from both anterior / posterior pituitary gland
- other functions
- controls effectors of Autonomic nervous system (cardiac + smooth muscle, glands)
- regulation of appetite
- regulation of thirst / water balance
- thermoregulation
- emotional reactions
- sleep wake cycles
- *
Outline the position and function of midbrain
- part of brain stem
- has nerve fibres that connect cerebrum with lower parts of brain and with spinal cord
- connects pons to diencephalon
- contains visual + auditory reflex centres
describe the structure and functions of the cerebellum
Involuntary control and coordination of planned skeletal muscle movement, to ensure movement is smooth, even and precise
also responsible for posture and balance
cerebellum receives and integrates sensory input from muscles, joints, eyes and ears
what is the corpus callosum
a tract of white matter (myelinated) that connects the two cerebral hemispheres
Outline function of Frontal lobe
Frontal -
motor areas (decide, plan and initiate somatic motor signals)
- Primary Motor cortex- receives input from other motor areas, plans and sends impulses to skeletal muscles (note- the motor area on RH controls voluntary muscle movement on Left side of body and vica versa)
- Broca’s area- controls muscle movements needed for speech
Association areas - receive, coordinate and interpret impulses from the sensory and motor cortices, enabling higher cognitive abilities
- premotor cortex- manual dexterity- coordinates movement initiated by primary motor cortex, ensuring learned patterns of movement can be repeated
-
Prefrontal cortex
- intellectual functions- associated with intelligence, cognition, memory, reasoning, personality
- motor functions - decides upon motor actions and relays to premotor cortex
Parietal- Sensory areas
Somatosensory area - where sensations of pain, temperature, pressure, proprioception are perceived
Right hemisphere perceives impulses from left side of body
- auditory (hearing)
- olfactory (smell)
- taste
- visual
occipital- sensory- visual cortex
what is the limbic system
Cerebrum + Diencephalon
“emotional brain”- control and regulation of emotions
receives input / send information to / from numerous areas of brain
examples of specific functions
- recognise anger + fear
- asess danger and regulate fear response
outline position and function of pons
- part of brainstem, lies between medulla oblongata and midbrain
- communication pathway between Cerebrum and cerebellum
- assist medulla with breathing rhythm
*
outline position and function of medulla oblongata
- part of brain stem, connects directly to spinal cord
- pathway for motor and sensory info - motor / sensory nerves descend from cerebrum and cross to other side to /from spinal cord (so left hemisphere controls right side of body, stimuli from left side of body goes to right hemisphere)
- CDV centre- controls blood pressure, and rate / force of cardiac contraction, and vasomotor control (constriction / dilation of blood vessels)
- Respiratory centres- controls rate + depth of breathing. works closely with pons
- regulates vomiting, coughing, sneezing, swallowing, hiccoughing
- reticular formation
What is function of spinal cord
- two way conducting system- provides neuronal pathways to / from the brain
- the communicating / syapsing region for afferent / efferent input
- most afferent sensory neurons synapse when they reach spinal cord
- most efferent motor neurons originate in spina cord
- site of integration for involuntary reflexes
What is function of spinal cord
- two way conducting system- provides neuronal pathways to / from the brain
- the communicating / syapsing region for afferent / efferent input
- most afferent sensory neurons synapse when they reach spinal cord
- most efferent motor neurons originate in spina cord
- site of integration for involuntary reflexes
Describe gross structure of spinal cord
- H shape - H is grey matter, surrounded by White matter
- Grey matter
- contains sensory, motor and interneurons that receive incoming / outgoing information and integrate. coordinates numerous reflex responses
- White matter
- contains bundles of axons called tracts that ascend up / descend down spinal cord
- ascending tracts take sensory input / descending tracts take motor input
What are 3 layers of meninges
- dura mater ( outermost, toughest layer)-
- arachnoid mater (middle layer) - contains CSF in subarachnoid space
- pia mater (innermost / delicate layer) - adheres directly to brain + spinal cord
