Biological Bases Flashcards
What does the size of the brain depend on?
How much energy the body consumes
Shape of brain
- the fact that we are standing up has made the brain stem underneath, rather than behind
- placement of eyes
Organisation of reptilian brain v mammalian brain
Reptile:
- striatum (move)
- thalamus (feel)
- superior colliculus (see)
- inferior colliculus (hear)
- brainstem (pons and medulla)
Mammal: have all of the above but before striatum we have:
- limbic system and the cerebral cortex
Breaking down the cerebral cortex
Occipital cortex (see) Temporal cortex (hear) Parietal cortex (feel) Motor cortex (move) Frontal cortex (act)
Anatomical directions
neuroaxis: perceived line through the centre of the nervous system –> indicates orientation of dorsal/ventral, anterior /posterior, medial/lateral
Dorsal v Ventral
above, below
Anterior or posterior
nose v tail
Lateral v medial
outside v inside
the planes
- sagittal (arrow through head)
- coronal (crown)
- horizontal
Nervous system tree
Peripheral:
- somatic
- autonomic (sympathetic, parasympathetic)
CNS:
- spinal cord
- brain
In the Central Nervous System
cerebrum
cerebellum
brain stem
spinal cord
Somatic nervous system
Voluntary system
- receiving sensory input from the environment and producing a motor output based on that sensory input
- does not include reflexes
Process of the somatic nervous system
- information coming from the environment via sensory receptors in the skin
- they go up through the dorsal roots (the back of the spinal column)
- comes up into the spinal column up into the brain
- information is processed and comes out as a motor output (through ventral roots, coming down into the muscle)
Talking about motor neurone disease
- nerves in the ventral roots, to the muscle, are degenerating
Peripheral nerves: groups
- cranial nerves
- cervical nerves
- thoracic nerves
- lumbar nerves
- sacral nerves
- coccygeal nerves
Cerebrum lobes (cortex)
- Frontal lobe: primary motor cortex
- Temporal lobe (side)
- Parietal lobe (top): primary somatosensory cortex
- Occipital lobe (back)
The frontal lobe and parietal lobe are separated by the central sulcus
Summarise the sommatic nervous system
- receives sensory input and delivers muscle output
- sensory input is received through dorsal roots to spinal cord
- motor output is delivered via ventral roots of spinal cord to muscle
- 6 areas that the nerves join the CNS (cranial, cervical, thoracic, lumbar, sacral, coccygeal)
- the brain receives sensory information at the somatosensory cortex and once processed in the brain, produces behaviour by modulating motor output from the primary motor cortex
Autonomic nervous system
Involuntary system
Sympathetic - extends from thoracic and lumbar spine
- short preganglionic nerves
- long postganglionic nerves
- involved in the 4 Fs (fright, flight, fight, fuck)
Parasympathetic - extends from cranium and sacral spine (craniosacral)
- long preganglionic nerves
- short postganglionic nerves
- digestion, growth, etc
both are usually active, but change intensity as the need arises
parallel systems that work in OPPOSITION to each other
Sympathetic nervous system effects:
- thoracic and lumbar
- increases heartrate, blood pressure, breathing
- reduces gastrointestinal function
Parasympathetic outflow
- cranial and sacral nerves
- Increasing gastrointestinal function
- Reducing heartrate, etc
Hormones
- hypothalamus + pituitary (many different hormones released directly into blood stream)
- pineal gland (melatonin)
- consider speed and range of effect –> the nervous system is faster (electrical signal) but the hormones are a lot slower and reach a lot more areas than the nervous system
Hypothalamus and pituitary gland
PG:
- anterior lobe: neurosecretery cells that release hormones (slower than the posterior) (growth hormone and adrienocorticotropic hormone)
- posterior lobe: neurons that go from hypothalamus down to posterior lobe to release hormones (this is faster than the anterior system) (includes vasopressin and oxytocin)
How is the brain protected / nourished
- the brain is highly vascularised (many arteries and veins) which maintain a constant fresh supply of oxygen and nutrients
The brain is protected with:
- Blood brain barrier (BBB):
- -> cerebrospinal fluid (CSF)
- -> meninges
- -> glial cells
Blood Brain Barrier (protection of the brain)
Blood brain barrier (BBB): little blood vessels on the inside and outside of brain only let certain things go from the blood vessels into the brain tissue (really tightly packed cells)
- brain capillary endothelial cells have continuous tight junctions
- only highly lipophilic drugs and small uncharged molecules can cross from blood capillaries to CSF by diffusion (O2, CO2, fat soluble molecules)
- important nutrients (amino acids and glucose) are actively transported by proteins in the capillary membrane (this requires energy)
What is the CSF
Cerebrospinal fluid and ventricles
- made up of water, a variety of salts (NaCl, KCl, CaCl2, MgSO4) and glucose
- ventricles are holes in the brain that help the CSF to flow around the brain
- CSF is made in those ventricles, goes down the spinal column and flows around the brain
- CSF is protective and has a lot of nutrients
- 3 meninges around the spinal cord are really important for the CSF to flow
Ventricles and CSF
- Cerebrospinal fluid is amde by the choroid plexus in the ventricles
- the ventricles and subarachnoid space circulate cerebrospinal fluid through and around the brain to provide nourishment
- there are 4 ventricles
- once CSF has circulated around the brain, it is reabsorbed by the arachnoid villi into venous blood (returns to heart)
White matter v Grey matter
white matter = myelinated axons
grey matter = nerve cell bodies
Sulcus v gyrus
sulcus is a valley / indent in the brain tissue
gyrus = hill in the brain tissue
Mapping out nervous system (same side, etc)
Ipsilateral = structures that lie on the same side
Contralateral = structures that lie on opposite sides
Proximal: structures that are close to one another
Distal: structures that are far from one another
What connects the hemispheres of the brain
the corpus callosum and anterior commissure
Terms referring to the nervous system:
tract = a set of axons within the CNS nerve = a sex of axons in the periphery nucleus = cluster of neuron cell bodies within the CNS ganglion = cluster of neuron cell bodies usually outside CNS
Frontal lobe functions
planning of movements, recent memory, some aspects of emotions
central sulcus
in front: precentral gyrus (primary motor cortex) which connects the frontal lobe
behind: postcentral gyrus (primary somatosensory cortex) which connects the parietal lobe
parietal lobe function
body sensations