Brain Anatomy PDF

Telencephalon develops into cerebrum Diencephalon: thalamus, hypothalamus Mesencephalon: midbrain (pons, medulla, brainstem) 4 major regions - Cerebrum - Folds - Dip up is gyri, dip down is sulci - Frontal lobe: primary motor cortex - Prefrontal cortex: high...

Telencephalon develops into cerebrum Diencephalon: thalamus, hypothalamus Mesencephalon: midbrain (pons, medulla, brainstem) 4 major regions - Cerebrum - Folds - Dip up is gyri, dip down is sulci - Frontal lobe: primary motor cortex - Prefrontal cortex: higher understanding - Precentral gyrus: moto - Postcentral gyrus: sensory - Central sulcus divides frontal and parietal lobe - Parietal lobe: sensory cortex - Angular gyrus: language comprehension - Temporal lobe: hearing - Lateral sulcus: separates frontal and parietal from temporal - Occipital lobe: sight - Association fibers: form connections within one hemisphere - Arcuate fibers: short, connect one gyrus to another - Projection fibers: form connections from one side of the brain to the other - Corpus callosum: acts as a bridge, for left and right hemisphere to communicate - Dopamine smooths out movement, fluid - Basal nuclei - Subconscious control of skeletal muscle tone - Cerebellum - Fine motor movements - Balance, posture - Regulates tone, muscle contraction - Vermis separates left and right hemisphere - Ataxia: disturbance in muscular coordination - Diencephalon -- gets signals from peripheral nerves - "roof" of the midbrain - Thalamus: main sorting center of the brain - Hypothalamus: controls hormones - Pineal body - Controls sleep, secretes melatonin - Superchiasmatic nucleus: regulates circadian rhythms - Brainstem (pons, medulla, spinal cord) - Reticular formation: involved in sleep/wake, consciousness - Cerebral cortex is top 5 millimeters of cerebrum - All conscious thought goes through this - Homunculus: mapping of brain - Located in frontal lobe - Controls speech Ventricles - Ventricles are lined with choroid plexus Cranial meninges - Dura mater - Folds - Falx cerebri: separates left and right lobes of cerebrum - Falx cerebelli: separates left and right lobes of cerebellum - Tentorium cerebelli: separates parietal and occipital lobe - Arachnoid mater - Subarachnoid space lies between arachnoid and pia mater - Pia mater - Attached to brain surface by astrocytes Blood Brain Barrier - Astrocytes - Basement membrane - Tight junctions - Macrophages Cerebrospinal fluid (CSF) - Surrounds all exposed surfaces of CNS - Brain floats in this - Circulates from choroid plexus through ventricle to canal of spinal cord into subarachnoid space Choroid plexus - Specialized ependymal cells surround capillaries - Choroid plexus produced CSF - Produced 500 mL a day - Removed waste products Medulla houses nuclei that is primarily involve in heart rate, respiration - The point of desiccation: point where the projection fibers cross Reflex centers: autonomic and reflex activity - Reticular formation - Gray and white matter with embedded nuclei - Regulates autonomic centers - Cardiovascular centers - Cardiac and vasomotor centers - Control blood flow through peripheral tissues - Respiratory rhythmicity centers - Set pace for respiratory movements - Pons house pneumotaxic and apneustic - Sensory and motor nuclei of cranial nerves - Nuclei and tracts that process and relay info sent to/from cerebellum - Midbrain - Tectum: dorsal (roof) - 2 pairs of sensory nuclei - Tegmentum: ventral (floor) - Substantia nigra: releases a neurotransmitter that is involved in motor movement -- dopamine - Limbic system - Establishes emotional states - Links conscious functions of cerebral corte with autonomic functions of brainstem - Facilities memory storage and retrieval Brain protection: skull meninges, BBB, and CSF Brain starts as a neural tube at 3 weeks Sensory = affecter, dorsal Motor = efferent, ventral - Dura mater joins the filum terminale in coccygeal ligament - Stretch reflex involved a single synapse and is the simplest reflex - Primary function of muscle spindles in regulate muscle length - A polysynaptic reflex involves ate least one interneuron between sensory and motor neurons - Anterior rami form nerve plexuses - White ramus innervate glands and smooth muscle - Posterior root contains the spinal ganglia - Somantic reflex controls the skeletal muscle contractions - Gray matter is primary involved in processing and integrating sensory and motor information - Sensory neurons are found in spinal ganglia - Denticulate ligaments are part of the pia mater - The lateral horn gray matter contains sympathetic neuron - Dorsal column carries sensory information about touch - Anterior ramus forms the nerve plexus - Visceral reflexes control glands and smooth muscle - Spinal reflexes are automatic and don't require brain involvement - Prosencephalon - Telencephalon = cerebrum - Diencephalon - Mesencephalon = remains - Rhombencephalon - Metencephalon = pons and cerebellum - Myelencephalon = medulla - Cerebrum's primary function is high cognitive functions - Precentral gyrus is involved in voluntary motor control - Corpus callosum connects the left and right hemisphere - Tectum contains sensory nuclei involved in vision and hearing - Blood-brain barrier is formed by tights junctions between endothelial cells - Filum terminale anchors spinal cord to vertebral column - Basal nuclei are involved in motor coordination - Pyramidal decussation is where projection fibers cross in the medulla - Medulla controls respiration - White matter is primarily involved in myelination of axons for faster communication Brainstem is the most inferior part of brain - three regions - Midbrain, pawns, medulla oblongata - cervical 7 vertebrae 8 nerves - cervical enlargement feeds nerves to upper limbs - thoracic 12 vertebrae and nerves - Lumbar 5 nerves and vertebrae - spinal cord ends between L1 and L2 - conus medullaris is the end of the spinal cord - lumbar enlargement feeds nerves to lower limbs and pelvis - Sacrum 1 vertebrae 1 coccygeal nerve Spinal nerves - 31 pairs 62 total - nerves that come out of the end of the spinal cord are cauda equina - each one has a white ramus communicator and a Gray ramus communicator that innervates glands and smooth muscle - Posterior ramus supplies skin and muscle of back - anterior ramus supply most of body wall skin and limbs - cns is made-up of brain and spinal cord processing centers - peripheral nervous system is made-up of nerves sensory input and motor response pathways Reflexes - quick automatic nerve responses triggered by specific stimuli spinal reflexes - controlled by the spinal cord alone without input from brain spinal cord - housed within protective membranes meninges, and vertebral column - Carries sensory and motor information between brain and most other parts of the body - About 18 inches long and 1/2 inch wide - Finishes growing at age 4 but vertebral column still grows - Central canal contains CSF - Transverse ridges: the sacrum when fused together has divisions - filum terminal: thin thread of fibers tissue at the end of the conus medullaris attached to coccygeal ligament spinal roots and ganglia - anterior root is axons of motor neurons - Posterior root are axons of sensory neurons - Spinal ganglia contains cell bodies of sensory neurons that form the posterior root spinal meninges - Dura mater - joins filum terminale in coccygeal ligament - epidural space is between vertebrae and dura mater - subdural space is deep to dura mater - arachnoid mater - Communication between the CNS and blood circulation - Subarachnoid space - filled with CFS that carries gases nutrients and waste - pia mater - directly attached to spinal cord and brain - denticulate ligaments - anchor spinal cord to dura mater provides stability - Gray matter: communication between cells - first layer of cerebrum - All conscious movement and thought goes to the Gray matter - Gray commissures - Narrow bands of grey matter around central canal - Tract: bundle of axons in CNS - ascending tracts: sensory information up towards the brain - descending tracks: motor commands down to the spinal cord - myelinated cells in cns: oligodendrocyte - unmyelinated cells in pns: Schwann cells Connective tissue layers surrounding spinal nerves - epineurium - surrounds the whole thing - perineurium - surrounds a bundle - endoneurium - surround individual axons peripheral distribution of spinal nerves - dermatomes: specific bilateral region of skin supplied by a single pair of spinal neurons - peripheral neuropathies: regional losses of neural function that affect dermatomes often from nerve trauma nerves plexuses - formed from blended fibers of anterior Rami of adjacent spinal nerve - no thoracic plexus - cervical plexus C1 to C5 - phrenic nerve: moves diaphragm - brachial plexus C5 to T1 - ulnar radial median - lumbar plexus T12 to L4 - femoral - sacral plexus L4 to S4 - Saitic nerve - Sensory neurons: bring info to CNS - motor neurons: sends commands from CNS out to peripheral effectors - interneurons: interpret plan and coordinate signals coming in and out neural reflexes - rapid automatic responses to specific stimuli - a specific reflex produces the same motor response each time types of reflexes - developmental - innate: basic neural reflexes formed before birth - acquired: rapid automatic learned motor patterns - motor - somatic: control skeletal muscle contractions - visceral: control other effectors - monosynaptic - single synapse: simplest reflex - stretch: Regulate skeletal muscle length through the body - polysynaptic - at least one interneuron between sensory neuron and motor neuron - muscle spindles: receptors in stretch reflexes postural reflexes - maintain upright posture plantar reflexes - normal in adult, reflexive toe curling Babinski reflex - normal in infants, big toe move upwards and others fan out Nervous system - Brain and spinal cord - Receptors of sense organs - Nervous tissue - Neurons for intercellular communication - Neuroglia (glia cells) CNS - Process and coordinate sensory data from inside and outside body - Motor commands control activities of peripheral organs - Higher functions of brain: intelligence, memory, learning PNS - Delivers sensory info to CNS - Carries motor commands to peripheral tissues - Nerves - Bundles of axons with connective tissues and blood vessels - Carry sensory info and motor commands - Afferent division: carries sensory information - Efferent division: carries motor information - Somatic - Controls skeletal muscle contractions - Both voluntary and involuntary (reflexes) - Autonomic - Controls subconscious actions, contractions of smooth and cardiac muscle and glandular secretions - Sympathetic division has a stimulation effect - Parasympathetic division has calming effect - Receptors: detect changes or respond to stimuli - Effectors: target organs that respond to motor commands Enteric nervous system - Initiates and coordinates visceral reflexes locally - Without instructions form CNS Neurons - Basic functional units of the nervous system - Send and receive signals - Cell body (soma) - Large nucleus and nucleolus - Perikaryon (cytoplasm) - Mitochondria (produce energy) - RER and ribosomes (synthesize proteins) Cytoskeleton of perikaryon - Neurofilaments and neurotubules - Similar to intermediate filaments and microtubules - Neurofibrils - Bundles of neurofilaments that provide support for dendrites and axons Nissil bodies - Dense areas of RER and ribosomes in perikaryon - Make nervous tissue appear gray (gray matter) Dendrites - Short and highly branched processes extending from cell body - Dendritic spines - Receive information from other neurons Axon - Single, long cytoplasmic process - Axolemma - Plasma membrane od the axon - Initial segment - Base of axon - Axon hillock - Thick region that attached initial segment to cell body - Collaterals - Branches of the axon - Telodendrion - Fine extensions of distal axon - Synaptic terminals - Tips of telodendrion Axon transport - Movement of materials between cell body and synaptic terminals - Move along neurotubules within axon Anaxonic neuron: all cell processes look similar Bipolar neuron - One dendrite and axon - Found in special organs Unipolar neurons - Axons and dendrites are fused - Most sensory neurons of PNS Multipolar neurons - Have one long axon and two or more dendrites - Common in CNS Sensory neurons - Unipolar - Cell bodies grouped in sensory ganglia - Somatic sensory neurons - Monitor external environment - Visceral sensory environment - Monitor internal environment Sensory receptors - Interceptors: monitor internal systems - Exteroceptors: monitor external systems - Proprioceptors: monitor position and movement of skeletal muscles and joints Motor neurons (efferent neurons) - Somatic motor neurons of SNS: innervate skeletal muscles - Visceral motor neurons of ANS - Innervate all other peripheral effectors - Smooth and cardiac muscle, glands, adipose tissue Interneurons - Most in brain and spinal cord, some in autonomic ganglia - Located between sensory and motor neurons - Distribution of sensory information - Coordination of motor activity - Involved in memory, planning, learning Neuroglia - Oligodendrocytes - Internodes -- myelinated segments of axons - Nodes (nodes of Ranvier) lie between internodes - Where axons may branch - White matter - Regions of CNS with many myelinated axons - Gray matter - Contains unmyelinated axons, neuron bodies, and dendrites Microglia - Clean up cellular debris, wastes, and pathogens - Wallerian degeneration: axon distal to injury degenerates - Schwann cells - Forms path for new growth - Warp around new axon - Nerve regeneration in CNS - Limited by astrocytes (star shaped) - Produce scar tissue - Release chemicals that block regrowth Synapse - Specialized site where a neuron communicates with another cell - Presynaptic neuron: sends the message - Postsynaptic neuron: receives message Electrical synapses - Direct physical contact between cells - Locked together by gap junctions Chemical synapses - Signals transmitted across a gab by neurotransmitters - Function - Axon terminal releases neurotransmitters that bind to postsynaptic plasma membrane Neurotransmitters - Chemical messengers contained within synaptic vesicles in axon terminal of presynaptic cell Cholinergic synapses - Release acetylcholine at all neuromuscular junctions involving skeletal muscle fibers Synaptic delay - Delay of.2-.5 m/sec occurs between arrival of action potential at axon terminals Synaptic fatigue - Occurs when neurotransmitters cannot be recycled fat enough to meet demands of intense stimuli Excitatory neurotransmitters - Cause depolarization of postsynaptic membrane Inhibitory neurotransmitters - Cause hyperpolarization of postsynaptic membrane Neuromodulators - Chemicals released by axon terminals that alter - Rate of neurotransmitters release - Or response by postsynaptic cell - Information is relayed in the form of action potentials - Neurotransmitters released at a synapse may have excitatory/inhibitory effect - Neuromodulators can alter rate of neurotransmitter release or response of a postsynaptic neuron