Neurons and the Brain Flashcards
What is part of the central nervous system?
Brain (forebrain, midbrain, hindbrain) and spinal cord
What is part of the peripheral nervous system? (structures)
Cranial nerves, spinal nerves, peripheral ganglia (cell bodies in periphery)
What are the two large divisions of the peripheral nervous system? And the divisions that fall below?
Somatic (conscious control): contains the motor (muscle control) and sensory (aware of senses, 5 main ones)
Autonomic (visceral, unconscious control): motor system like heart beating (sympathetic and parasympathetic) and sensory (sensations from guts)
What is the two motor divisions of the autonomic nervous system?
Sympathetic: fight/flight, HR/BP increase, pupils dilate, glands shut down, bronchi dilate to get more O2
Parasympathetic: rest/digest, HR/BP decrease, pupils normal, bronchi constrict back to normal
What are the two cells in the nervous system?
Neurons: nerve cells that conduct signals
Neuroglia: support cells for the neurons
What are some features of neurons (facts)? (2)
The brain has 100 million neurons
Neurons form connections to other cells via synapses (10^15 synapses, each neuron has about 100,000 connections with other neurons)
What are the two types of nerve cell bodies?
Nucleus: collection of nerve cell bodies within the CNS
Ganglion: collection of nerve cell bodies within the PNS
What are the structures of the neurons from dendrites to axon hillock?
Dendrites, cell body (contains the nucleus, nucleolus, Nissl bodies, mitochondria), neurofibrils provide structural support for axon hillock and axon hillock has the initial segment which makes decision if cell will fire an action potential
What are the neurons structures below the axon hillock?
Axon: 1 per cell
Axon collateral: branches of the axon
Myelin sheath: insulator and increase speed
Schwann cells make myelin in PNS
Axon terminal
Synaptic bouton
What are the three types of inputs that come from the Initial segment?
Excitatory input
Inhibitory input
And then the summation of both into the threshold potential and the cell fires
What are the three different classes of neurons?
Multipolar: normal neuron, multiple projections from one cell body
Unipolar: 1 appendage from cell body, usually sensory\
Bipolar: 2 appendages from cell body, RARE, found in special senses (5 senses)
What are the two other types of special neurons/cells?
Pyramidal cell: predominant cell type in cerebral cortex
Purkinje cell: cerebellum, complex dendritic tree because compares what you want to do and what you are doing, controls and corrects motion (move smooth)
What are the two types of neuroglia found in the PNS?
Satellite cells: surround neuron cell bodies in ganglia, regulate O2, CO2, nutrient and NT levels around neurons in ganglia
Schwann cells: surround all axons in the PNS, responsible for myelination of PNS axons, participate in repair process after injury
What are the four types of neuroglia found in the CNS?
- Oligodendrocytes: myelinate CNS, provide structure framework, filipodium attach one ODC to many axons
- Astrocytes: maintain BBB, structural support, regulate nutrient and dissolved gas, absorb and recycle NT, form scar
(reactive astrocytes help with spinal cord damage to form scar tissue but this means new axons cannot grow and repair) - Microglia: remove cell debris, wastes and pathogens by phagocytosis
- Ependymal cells: line ventricles and central canal, assist producing, circulating, and monitoring of CSF
What are the two structures that protect the CNS?
Meninges: cover and protect the CNS
- Dura mater: tough outer layer
- Arachnoid mater: CSF
- Pia mater: intimate contact with brain, cannot peel it off
CNS floats in cerebrospinal fluid (cushioning during accel)
What are the brain layers starting at the scalp?
Scalp, pericranium (connective tissue), calvaria (skull cap), dura mater, arachnoid mater, pia mater, brain
What does the arachnoid layer look like?
Sarrann wrap with blood vessels
What are the three main parts of the brain?
Cerebrum (shaped like a bum)
Cerebellum (shaped like a bell)
Brain stem (shaped like a stem)
What are the 5 functions of the cerebrum?
Higher cognitive functions (thought, intellect, planning, creativity)
Language and speech (formulation and comprehension)
Somatic motor function (regulates skeletal activity and coordinates movement through BG)
Somatic sensory function (interpret stimuli from the environment)
Regulates the emotional aspects of behaviour
What is the structure of the cerebrum?
2 hemispheres, 4 lobes, 3 poles, 3 major grooves, many sulci and gyri
Cerebral cortex: grey matter (neuronal cell bodies)
Cerebral medulla: white matter (axons)
What are the three major grooves, 4 lobes, 2 hemis, and 3 poles in the cerebrum?
Hemis: left and right
Poles: frontal, temporal (x2), occipital
Grooves: longitudinal fissure, central sulcus, lateral sulcus
Lobes: frontal, occipital, parietal, temporal
What are the roles of the 4 lobes of the brain?
Frontal: higher cognitive, planning, strategy, motor
Parietal: perception of self in space, sensory
Temporal: memory, learning, social, hearing
Occipital: vision
What are the two gyri that line the central sulcus?
Precentral gyrus: primary motor cortex (frontal)
Postcentral gyrus: primary somatosensory cortex (parietal)
What is the motor homunculus? How many are there?
2, one in each hemisphere
Exists in the precentral gyrus (primary motor)
Lots of cortex devoted to hand (upper extremity) because lots of control in movement, same with face
Representation of body parts with more cortex dedicated to them
What is the sensory homunculus? How many are there?
2, one in each hemisphere
Exists in postcentral gyrus (primary sensory)
Representation of the amount of cortex dedicated to sensory movements
Lots in face and hands
What is the reason why no organs are represented in the sensory homunculus?
NO ORGANS (visceral structures): innervated by spinal cord levels, sensory info to brain in form of spinal cord levels therefore pain manifests in the body areas that are also linked to those spinal cord levels (pain in body wall)
What is contained in the grey and white matter?
Grey matter: in cortical region, cell bodies
White matter: in medulla, myelinated axons due to phospholipids (FAT) that are white
What are the three types of fibre tracts in the brain?
Projection fibres: travel to and from cortex (sense, motor)
Association fibres: intrahemi connections, short OR long, can be within lobe or between lobes (Broca’s/Wernicke’s)
Commissural fibres: interhemi connections between RT and LT, corpus callosum between them
What are the 4 characteristics of the cerebellum?
Acts as a comparator: compares intended movement and evolving movement and corrects for errors
Ensures movements are smooth, coordinated and purposeful (skilled)
Regulates posture and balance
Disease: cerebellar ataxia (intention tremor, lack of balance and coordination)
What are the three structures in the brainstem?
Midbrain, pons, medulla oblongata (this also goes from highest to lowest)
What structures lie above the midbrain?
Diencephalon (thalamus, hypothalamus)
What are the 5 characteristics of the brainstem?
Contains motor/ sensory pathways connecting cerebral cortex and thalamus to spinal cord
Houses cranial nerve nuclei (origins of the CNs)
Contains the reticular activating system: important for arousal of cortex and consciousness
Vital centers for regulating heart rate and breathing
Centers for swallowing and gag reflex regulation
What are the four things contained in the midbrain?
Substantia nigra: regulates motor activity, neuronal degeneration leads to Parkinsons
Red nucleus: regulates motor activity
Relay centers for visual and auditory pathways
Cranial nerves III and IV attached to it
What is contained within the pons?
Bridge between cerebrum and cerebellum
Cranial nerves V, VI, VII, VIII attached to it
What is contained within the medulla?
Contains vital cardio-respiratory regulatory centers
Cranial nerves IX, X, XI, XII
What are the 4 ventricles of the brain? How does the CSF get into the spine?
Lateral ventricles: in LT and RT hemispheres, have anterior horn in frontal lobe, posterior horn into occipital lobe and inferior horn into the temporal lobe
Third ventricle: between thalamic lobes
Fourth ventricle: between pons and cerebellum
Gets into the spinal cord via the central canal
Cannot see lateral ventricles because deep in the brain
What are the 3 cerebral arteries and what do they feed?
Anterior cerebral artery: midsagittal surface supply
Middle cerebral artery: ICA moves here, lateral blood supply
Posterior cerebral artery: posterior blood supply
What does the basilar artery and vertebral artery do?
Basilar artery: anterior to pons, bifurcates into LT/RT posterior cerebral artery
Vertebral artery: posterior blood supply enter by foramen magnum and form basilar
What do the two communicating arteries do?
Posterior communicating artery: LT/RT between posterior and middle cerebral artery
Anterior communicating artery: between 2 anterior cerebral
What is the Circle of Willis?
Circle of blood vessels around the base of the brain therefore shunting blood from one place to another during injury
