Brain anatomy Flashcards
What are the parts of the nervous system?
- central
- peripheral
What are oligodendrocytes?
- glial cell
- in CNS
- creates myelin
What are Schwann cells?
- in PNS
- create myelin
- once cell makes one myelin sheath
What is extracellular fluid?
- flows around cells providing nutrients and collecting waste
- collected into lymph vessels, which carries it to lymph nodes & lymph organs
What is the lymphatic system?
- part of the immune system that detects and destroys invading organisms and foreign particles
- Liquid in the lymphatic system (lymph) is returned to the blood supply to start the process again
What is the blood brain barrier?
- CNS does not participate in the lymphatic system of the body because there are no holes in the blood vessels that pass through the brain and spinal cord
What is cerebrospinal fluid?
- the brain makes its own extracellular solution by actively picking out exactly what it needs from the blood
What makes up the CNS?
- brain
- spinal cord
- projection neuron
- interneuron
What is a projection neuron?
- has an axon that innervates distal areas of the brain
- it synapses on neurons that are far away from where the axon started
- mostly release glutamate
What is an interneuron?
- only synapses on local, nearby neurons
- axon doesn’t go far
- mostly release GABA
What are the parts of the PNS?
- outside brain and spinal cord
- axons of motor neurons
- sensory neuron dendrites, axons and cell bodies
What are axons of motor neurons?
- efferent fibers (outputs)
- bringing information away from the CNS
- Motor neurons control muscle contraction and gland secretion
- Motor neuron cell bodies are mostly located in the spinal cord
What are the axons of sensory neurons
- afferent fibers (inputs)
- bringing information towards the CNS
- Sensory neurons detect changes in the external and internal environment
- The axons of sensory neurons synapse in the CNS
What are nerves?
- enclosed, cable-like bundles of axons in the peripheral nervous system
- bundle of bundles of axons
- mix of sensory axons and motor axons
What are spinal nerves?
- 31 pairs
- axons of spinal nerves enter/leave the spinal cord
What are cranial nerves?
- 12 pairs
- enter/leave the brain directly
- All cranial nerves (except for one) process movements and sensory information around the head and neck
- exception is the 10th cranial nerve – the vagus – which branches extensively in the upper half of the body
What is the spinal cord?
- long, conical structure
- bring sensory information to the brain and to bring motor fibers to effector organs throughout the body
- various reflexive control circuits are located there
What is the anterior direction?
- in front
What is the posterior direction?
- behind
What is the superior direction?
- above
What is the inferior direction?
- below
What is the rostral direction?
- towards the beak
What is the caudal direction?
- towards the tail
What is the dorsal direction?
- towards the back (or top of head
What is the ventral direction?
- towards the belly
What is the lateral direction?
- away from the midline
What is the medial direction?
- towards the midline
What is the neuraxis?
- imaginary line that runs along the length of the CNS
How does the PNS divide?
- somatic
- autonomic
What is the somatic system?
- Interacts with external environment
- Afferent nerves carry sensory signals from the body’s surface TO the CNS
- Efferent nerves carry motor signals FROM the CNS to skeletal muscles
What is the autonomic system?
- Regulates body’s internal environment
- Afferent nerves carry sensory signals
from internal organs TO the CNS - Efferent nerves carry motor signals FROM the CNS to internal organs
What are the parts of the efferent autonomic system?
- sympathetic
- parasympathetic
What is the sympathetic division?
- Primes the body for action
- fight-flight-freeze response
- always active to some extent
- regulates heart rate, blood flow, and the activity of nearly every organ
- When strongly stimulated, it increases blood flow to organs involved in intense physical activity and shunts blood away from organs that are not necessary for immediate survival
What is the parasympathetic division?
- Supports activities that occur when the body is in a relaxed state
- always active to some extent
- regulates urination, defecation, salvation, and sexual arousal, increasing the body’s energy stores (digestion)
- feed and breed, rest and digest
What are the major anatomical divisions of the brain?
- forebrain
- midbrain
- hindbrain
What are the principle structures of the hindbrain?
- medulla oblongata
- pons
- cerebellum
What are the principle structures of the midbrain?
- tectum
- tegmentum
What are the principle structures of the forebrain?
- hypothalamus
- thalamus
- limbic system
- basal ganglia
- cerebral cortex
What do the medulla and pons do?
- Internal sensations (stretch) and internal muscles (heart, bladder) are generally processed in the medulla & pons
- several cranial nerve nuclei in the medulla and pons, which participate in hearing, balance, taste, and sensations and movements of the face
What is brain nuclei?
- in the brain, the word nuclei refers to a collection of neurons that are clustered together that regulate a shared function
What is contralateral?
- structures on the opposite side of the body
What is ipsilateral?
- structures on the same side of body
- taste and smell
What is superficial?
- located close to the surface
- close to exterior
What is deep?
- located far away from the surface
- deep in interior
What is proximal?
- nearby
What is distal?
- far away
What makes up the brain stem?
- medulla
- pons
- midbrain
What is the medulla oblongata?
- contains a collection of brain nuclei that regulate autonomic functions, such as heart rate, blood flow, breathing, vomiting, sneezing, etc
What are two parts of the medulla?
- area postrema
- reticular formation
What is the area postrema?
- initiates vomiting when poisons are detected
- blood–brain barrier is noticeably weak here
What is the reticular formation?
- regulates sleep and arousal
What are the pons?
- bulge in the brain stem that relays information between the cerebrum and cerebellum
- cranial nerve nuclei are located; participate in hearing, balance, taste, facial movements, and sensations of the face
- Part of the reticular formation is also here
What is the cerebellum?
- little brain
- contributes to the coordination, precision, and accurate timing of movements
- sensorimotor integration on the timescale of milliseconds/seconds, which exerts a smoothing effect on movement and cognition
- plays an important role in motor learning, particularly as the body grows and changes over time
What does cerebellar damage result in?
- jerky, exaggerated, poorly coordinated movements
- extensive cerebellar damage makes it impossible to stand up
What do neurons in the cerebellar cortex do?
- send axons inwards to the deep cerebellar nuclei
- from there, neurons project to the brain and spinal cord
What is the midbrain?
- collection of nuclei that orchestrate complex reflexive behaviours
- consists of the tectum and tegmentum
What is the tectum?
- roof
- two pairs of bumps on the dorsal surface of the midbrain
What is the superior colliculi?
- top 2 bumps of the tectum
- involved in orienting the animal to things in peripheral vision
What is the inferior colliculi?
- bottom 2 bumps of the tectum
- involved in orienting to unexpected sounds
What is the tegmentum?
- several structures that coordinate and motivate complex species-typical movements
- some areas process pain and orchestrate behavioural responses to threats
What are the areas in the forebrain and hindbrain that are similar?
- cerebral cortex -> cerebellum
- thalamus -> pons
- hypothalamus -> medulla oblongata
What is the hypothalamus?
- bilateral structure made up of several nuclei, which generally regulate autonomic nervous system activity
- involved in behaviours that directly relate to survival
- link the nervous system to the endocrine system (release of hormones into the blood stream) via the pituitary gland
- master regulator of hormone system
What is a hormone?
- chemical substance that is released into the blood by an endocrine gland
- it has effects on cells in other organs
What is an endocrine gland?
- gland that secretes hormones into the blood
- master regulator of the endocrine system is the hypothalamus, as it releases hormones that regulate the function of other endocrine glands
What is the thalamus?
- bilateral structure that contains several nuclei, many of which relay ascending sensory information to different regions of the cerebral cortex
- many nuclei of the thalamus have widespread cortical projections
- directs information
What is the cerebral cortex?
- where sensory information enters conscious awareness
- where our understanding of the world is formed
- where we decide how to purposefully move in the world
- multi-layered structure
- Neurons are interconnected between layers in a way that gives rise to cortical columns, which are thought to be partially distinct functional units
What is the surface of the brain?
- the cerebral cortex
- it contains sulci, fissures, and gyri
- these convolutions increase the surface area of the cerebral cortex
What are sulci?
- small grooves
What are fissures?
- large or major grooves
What are gyri?
- ridges between sulci or fissures
What is gray matter?
- outermost portion of the cerebral cortex
- there is high concentration of cell bodies here
What is white matter?
- beneath the gray matter
- primarily just myelinated axons
What are the different ways of cutting the brain?
- coronal cut
- sagittal cut
- horizontal cut
What is a coronal cut?
- separating the front from the back of the brain
What is a sagittal cut?
- a mid-sagittal cut means the exact middle
- between the eyes
- separating left from right
What is a horizontal cut?
- separating the top from the bottom
What is medial?
- toward midline
What is lateral?
- away from midline
What are the 4 lobes of the cerebral cortex?
- frontal
- parietal
- temporal
- occipital
What is the frontal lobe?
- controls movement
What is the parietal lobe?
- processes touch information
What is the temporal lobe?
- processes auditory information
What is the occipital lobe?
- processes visual information
Where are taste and smell processed?
- near the junction of the frontal, parietal, and temporal lobes inside the lateral fissure
Where is taste processed?
- in the insular cortex
Where is smell processed?
- in the piriform cortex?
What is the longitudinal fissure?
- separates the two hemispheres
What is the lateral fissure?
- separates the frontal lobe and the temporal lobe
What is the central sulcus?
- separates the frontal lobe and the parietal lobe
What is the corpus collosum?
- large bundle of axons that connects corresponding parts of the left and right hemispheres
- two cerebral hemispheres perform somewhat different functions, perceptions and memories are unified
What are the primary cortical areas?
- primary motor cortex
- somatosensory cortex
- primary auditory cortex
- primary visual cortex
Where is the primary motor cortex?
- frontal lobe
Where is the somatosensory cortex?
- parietal lobe
Where is the primary auditory cortex?
- temporal lobe
Where is the primary visual cortex?
- occipital lobe
What is the primary motor cortex?
- contains motor neurons that synapse in the spinal cord
- different regions of primary motor cortex control different parts of the body
What is the somatosensory cortex?
- where touch information enters the cerebral cortex
- different regions of somatosensory cortex receive information from different parts of the body
What is the primary auditory cortex?
- where auditory information enters the cerebral cortex
What is the primary visual cortex?
- where visual information enters the cerebral cortex
What is the insular cortex?
- hidden in lateral fissure
- where gustatory information enters the cerebral cortex
What happens if a primary area is damaged?
- lose conscious awareness of that information
What is a sensory association cortex?
- adjacent to each primary sensory area
- where perception takes place and memories are stored
What are the sensory association cortexes?
- premotor cortex
- somatosensory association cortex
- auditory association cortex
- visual association cortex
What happens if the sensory association cortex is damaged?
- can’t label what is being sensed
What are meninges?
- 3 protective layers of tissue that wrap the brain and spinal cord
What protects the CNS?
- meninges
- bone (skull and vertebrae)
What are the 3 types of meninges?
- dura matter
- arachnoid membrane
- pia matter
What is dura matter?
- the outer layer
- thick, tough, unstretchable tissue
What is the arachnoid membrane?
- the middle layer
- web-like extensions (arachnoid trabeculae) create a soft, spongy layer that is filled with cerebrospinal fluid
What is pia matter?
- the third layer
- sits closest to the brain and is a bit like Saran-Wrap
What do large blood vessels do in the CNS?
- course through the subarachnoid space (arachnoid trabeculae)
What do smaller blood vessels do in the CNS?
- capillaries branch off and dive into the brain to provide nutrients and oxygen
What is cerebrospinal fluid?
- brain floats in it
- made from blood by tissue called choroid plexus, which are in each of the brain’s four ventricles
- made continuously
- fully exchanged about 4 times per day
- circulates around and into the brain providing nutrients and removing waste
- exits the CNS by passing through holes in the dura mater, where it is absorbed into the blood supply
What are ventricles?
- the interconnected hollow spaces in the center of the brain
What are the 4 ventricles of the brain?
- 2 lateral ventricles
- third ventricle
- fourth ventricle
Where are the 2 lateral ventricles?
- sit underneath the cerebrum (cerebral cortex)
Where is the third ventricle?
- lies between the two thalamic nuclei at the center of the brain
What is the cerebral aqueduct?
- a long, tube-like structure that connects the third and fourth ventricle
Where is the fourth ventricle?
- in the hindbrain, between the pons and cerebellum
What is the central canal of the spinal cord?
- connects to the fourth ventricle
What is the cerebral cortex?
- contains 4 lobes
- each lobe has a Primary Area
- other ares are Association Cortex
What is a primary area?
- where information leaves/enters the cerebral cortex
What is an association cortex?
- where we interpret sensory information and plan movements
What are subcortical structures?
- sit beneath the cerebral cortex
- basal ganglia and limbic system
What is the basal ganglia?
- a collection of nuclei
- they regulate intentional movements, motivation, reinforcement learning, and habits
Where is the basal ganglia?
- located beneath the lateral ventricles
What are the inputs of the basal ganglia?
- inputs come from all over the forebrain
- strong dopamine input from the midbrain
What are the outputs of the basal ganglia?
- outputs of the basal ganglia descend to midbrain and hindbrain to regulate movement
- other outputs ascend to the cerebral cortex (via the thalamus) to regulate sensory processing and decision making
What happens when the basal ganglia dysfuntions?
- neurological (movement) disorders are associated with basal ganglia dysfunction
- Parkinson’s disease relates to the loss of dopamine signaling in the basal ganglia
What is the limbic system?
- collection of subcortical brain areas that regulate emotions and the formation of episodic memories
- hippocampus, amygdala, and cingulate cortex
What is the cingulate cortex?
- large area that overlies the corpus callosum
- interconnects many limbic areas of the brain
What is the hippocampus?
- hidden in the temporal lobe
- critical for explicit memory formation
What is the amygdala?
- hidden in the temporal lobe
- critical for processing emotion, especially fear
How does the brain develop?
- hollow, enclosed neural tube forms during the first month of human development in the womb
- first cells in this tube are neural progenitor cells
- until the 8th week of development, these cells only undergo symmetrical cell division
- asymmetrical cell division starts around the 8th week of development
- 3 months
- end of the fifth month, there are 85 billion neurons in the human brain
- many of these neurons die before birth
What is symmetrical cell division?
- each neural progenitor cell becomes two neural progenitor cells
What is asymmetrical cell division?
- when a neural progenitor cell divides, one of the daughter cells migrates away from the center of the neural tube
- next time that cell divides, it will produce either two neurons or two glia cells
What is neurogenesis?
- Production of new neurons
- Neural progenitor cells produce neurons and glia after they undergo asymmetrical cell division
- Human neurogenesis largely stops five months after conception when neural progenitor cells undergo apoptosis
- There may be a little neurogenesis in some adult mammals, but whether this occurs in humans is controversial
What is apoptosis?
- programmed cell death that occurs in multicellular organisms
- highly regulated and controlled form of cell suicide that ensures a dying cell does not cause problems for its neighbours
- human neural progenitor cells undergo apoptosis around the fifth month of development in the womb
- when (most or all) neurogenesis stops
