BIO MIDTERM

• Brain


  Soft whitish-gray organ that is anatomically continuous with spinal cord, resides in cranial cavity and directly or indirectly controls most of body's functions, made of mostly nervous tissue with epithelial and connective tissues, contains internal cavities called ventricles filled with cerebrospinal fluid

  
• Divisions of the brain

  • Cerebrum
  • Diencephalon
  • Cerebellum
  • Brainstem

  
• Brain


  • Contains white matter with myelinated axons
  • Contains gray matter with neuron cell bodies, dendrites, and unmyelinated axons

  
• Gray matter


  Located in cerebrum's outer region and scattered throughout its deeper portions
• White matter


  Bundles of axons (tracts) that receive input from and send output to clusters of cell bodies and dendrites in cerebral gray matter (nuclei)
• Protective features of the brain

  • Cranial meninges
  • Cerebrospinal fluid (CSF)
  • Blood-brain barrier

  
• Cranial meninges


  Three layers of protective membranes that surround the brain

  
• Cerebrospinal fluid (CSF)


  Fluid that bathes the brain and fills the cavities
• Blood-brain barrier


  Prevents many substances from entering the cells of the brain
• Endothelial cells in blood-brain barrier

  • Have more tight junctions than typical capillary
  • Limited capacity for exocytosis and exocytosis

  
• Nervous system


  • Controls our perception and experience of the world
  • Directs voluntary movement
  • Is the seat of consciousness, personality, learning, and memory
  • Regulates many aspects of homeostasis along with endocrine system, including respiratory rate, blood pressure, body temperature, sleep/wake cycle, blood pH
• Substances that easily pass through plasma membranes are able to pass through blood-brain barrier (H2O, O2, CO2, nonpolar, lipid-based molecules)
• Structural divisions of the nervous system

  • Central Nervous System (CNS)
  • Peripheral Nervous System (PNS)

  
• Protein channels or carriers allow for passage of other essential molecules across blood-brain barrier (glucose, amino acids, ions)
• Central Nervous System (CNS)


  • Includes the organs brain and spinal cord

  
• Most large, polar molecules effectively prevented from crossing blood-brain barrier in any significant amount
• Peripheral Nervous System (PNS)

  • Consists of organs called nerves and their branches

  
• Special senses


  Convey specific stimuli from specialized sensory organs in discrete locations in the head

  
• Cerebrum


  Enlarged superior portion of brain responsible for higher mental functions and has roles in sensation and movement, divided into left and right cerebral hemispheres

  
• Brain


  • Enclosed in skull
  • Composed primarily of nervous tissue, with billions of neurons (nerve cells)
• Special senses


  • Smell (olfaction)
  • Taste (gustation)
  • Vision
  • Hearing (audition)
  • Vestibular sensation

  
• Sulci


  Shallow grooves on surface of cerebrum
• Spinal cord


  • Enables brain to communicate with most of body below head and neck
  • Begins at foramen magnum; continues through vertebral foramina of C1 to L1/L2
  • Contains neurons; much fewer than brain

  
• Olfaction


  Olfactory system allows for detection of odorants (chemicals in the air). Neurons in olfactory system transduce odorants into electrical signals that our brain can interpret.

  
• Gyri


  Elevated ridges found between sulci
• Nerves


  • Main organs of PNS; carry signals (nerve impulses) to and from CNS
  • Consist of axons of neurons bundled together with blood vessels and sheaths of CT

  
• There are over 100 known neurotransmitters known to operate in the human nervous system

  
• Humans can smell ~400K odorants (~80% are unpleasant odors)
• Nerves classified based on origin or destination

  • Cranial nerves - 12 pairs of nerves traveling back to or from brain
  • Spinal nerves - 31 pairs of nerves traveling back to or from spinal cord

  
• Fissures


  Deeper grooves that separate large regions of the cerebrum
• Olfactory epithelium


  • Small region of specialized epithelium in superior nasal cavity
  • Contains olfactory neurons, basal cells, and supporting cells

  
• Neurotransmitters


  • They are diverse in structure and function

  
• Functional divisions of the nervous system

  • Sensory
  • Integrative
  • Motor

  
• Lobes of the cerebrum

  • Frontal
  • Parietal
  • Temporal
  • Occipital
  • Insula

  
• Olfactory neurons


  Modified bipolar neurons that function as chemoreceptors which allow detection of odorants. Each contains an exposed dendrite that projects into the roof the nasal cavity, with an expanded tip containing nonmotile olfactory cilia which contains receptors that bind to odorants.

  
• Neurotransmitter receptors


  Neurotransmitters induce either an IPSP or EPSP by binding to receptors in the membranes of postsynaptic neurons

  
• Sensory functions


  Gather info about internal and external environments of body
• Central sulcus


  Separates the frontal lobe from the parietal lobe

  
• Autonomic nervous system (ANS)


  The involuntary arm of the peripheral nervous system; also called the visceral motor division

  
• Olfactory pathway


  1. Bundles of unmyelinated axons of olfactory neurons project through cribriform plate, forming the olfactory nerve (CN I)

  2. Olfactory nerves terminate in the brain in paired masses of gray matter called the olfactory bulbs

  3. Within the olfactory bulbs, the axons of olfactory neurons synapse with mitral cells

  4. Axons of mitral cells form the olfactory tract

  5. Olfactory tract carries olfactory info to the primary olfactory cortex in temporal lobe where conscious awareness of smell begins

  6. Neurons in olfactory cortex then send signals to amygdala, hippocampus, hypothalamus, and components of limbic system; evokes emotional and visceral responses to odors

  7. Signals are also sent to frontal lobe; thought to play a part in integrating olfaction and taste