the brain
DESCRIPTION
I-XII pairs of cranial nerves, their functional division into three groups. Organ of vision. Coats of the eyeball and refractile environment. The Brain. 3 primary divisions: Forebrain cortex (folded stuff) limbic system, etc (stuff around brain stem) Midbrain (top of brainstem) - PowerPoint PPT PresentationTRANSCRIPT
I-XII pairs of cranial nerves, their functional division into three groups. Organ of vision. Coats of
the eyeball and refractile environment.
• 3 primary divisions:– Forebrain
• cortex (folded stuff)• limbic system, etc (stuff around brain stem)
– Midbrain (top of brainstem)
– Hindbrain (bottom of brainstem + cerebellum)
The Brain
Organ of vision. Coats of the eyeball and refractile environment.
Hindbrain
Medulla
Pons
Cerebellum
http://www-unix.oit.umass.edu/~psyc335c/lectures/hindbrain.gif
Pons
MedullaCerebellum
Medulla:Controls vital reflexes: breathing, heart rate, vomiting, salivation, coughing, sneezing
- Via cranial nerves
Damage to medulla can be fatal
Large doses of opiates can be fatal b/c suppress activity of medulla…why…?...b/c receptors there!
Pons:Also has cranial nerves
Location of axon decussation (where axons cross from one side of the brain to the other…so left brain controls right body and vice versa)
Reticular formation: motor control, arousal, consciousness
Midbrain:Cerebral aqueduct
More cranial nerves
Superior colliculus (visual info)
Inferior colliculus (auditory info)
Substantia nigra: dopamine-producing cells, structure that is lost in Parkinson’s Disease
http://en.wikipedia.org/wiki/Midbrain
BrainstemMedulla
Pons
Midbrain
Some forebrain structures
Senses: Information comes in the cranial nerves and eventually ends up in the cortex
Cranial Nerves
http://www.besthealth.com/besthealth/bodyguide/reftext/images/cranial_nerves.jpg
Table 4.4, page 87
Olfactory nerve:
Smell
Cranial Nerves
http://www.besthealth.com/besthealth/bodyguide/reftext/images/cranial_nerves.jpg
Table 4.4, page 87
Optic nerve:
Vision
Cranial Nerves
http://www.besthealth.com/besthealth/bodyguide/reftext/images/cranial_nerves.jpg
Table 4.4, page 87
Occulomotor nerve:
Eye movement, pupil constriction
Cranial Nerves
http://www.besthealth.com/besthealth/bodyguide/reftext/images/cranial_nerves.jpg
Table 4.4, page 87
Trochlear nerve:
Eye movement
Cranial Nerves
http://www.besthealth.com/besthealth/bodyguide/reftext/images/cranial_nerves.jpg
Table 4.4, page 87
Trigeminal nerve:
Skin senses from face
Jaw muscles for chewing and swallowing (muscles of mastication)
Cranial Nerves
http://www.besthealth.com/besthealth/bodyguide/reftext/images/cranial_nerves.jpg
Table 4.4, page 87
Abducens nerve:
Eye movements
Cranial Nerves
http://www.besthealth.com/besthealth/bodyguide/reftext/images/cranial_nerves.jpg
Table 4.4, page 87
Facial nerve:
Taste
Facial expressions
Crying
Salivation
Dilation of head’s blood vessels
Cranial Nerves
http://www.besthealth.com/besthealth/bodyguide/reftext/images/cranial_nerves.jpg
Table 4.4, page 87
Acoustic nerve:
Aka vestibulocochlear or statoacoustic
Hearing
Equilibrium
Cranial Nerves
http://www.besthealth.com/besthealth/bodyguide/reftext/images/cranial_nerves.jpg
Table 4.4, page 87
Glossopharyngeal nerve:
Taste
Swallowing
Salivation
Throat movements during speech
Cranial Nerves
http://www.besthealth.com/besthealth/bodyguide/reftext/images/cranial_nerves.jpg
Table 4.4, page 87
Vagus nerve:
Sensation from neck and thorax
Control of throat, esophagus, larynx
Parasympathetic nerves to stomach, intestines, etc
Cranial Nerves
http://www.besthealth.com/besthealth/bodyguide/reftext/images/cranial_nerves.jpg
Table 4.4, page 87
Spinal accessory nerve:
Aka Accessory nerve
Neck and shoulder movements
Cranial Nerves
http://www.besthealth.com/besthealth/bodyguide/reftext/images/cranial_nerves.jpg
Table 4.4, page 87
Hypoglossal nerve:
Muscles of tongue
Forebrain
• Thalamus
• Hypothalamus
• Pituitary gland
• Basal ganglia
• Basal forebrain
• Hippocampus
• Limbic system
Thalamus:
Relay station for all sensory info on its way to brain (except olfactory info)
Many specialized nuclei (ex: LGN, MGN…don’t have to know these!)
Hypothalamus
Communicates with pituitary gland to alter hormone release
Involved in feeding, drinking, temperature regulation, sexual behavior, fighting, arousal (activity level)…4 Fs
Pituitary gland
Endocrine gland (hormone producing)
Attached to base of hypothalamus by stalk
Makes and releases hormones into bloodstream
http://www.uni.edu/walsh/basalganglia-2.jpg
Basal Ganglia
Motor control, but also memory and emotional expression
Lose dopamine neurons in SN Parkinson’s Disease
Lose dopamine neurons in caudate & putamen Huntington’s chorea
thalamus.wustl.edu/ course/cbell6.gif
Don’t memorize image!!! Just understand that this is a very complex system!
http://memorylossonline.com/summer2003/glossary/basalforebrain.jpg
Basal forebrain
Anterior and dorsal to hypothalamus
Important for arousal, wakefulness, attention
Lose cells in nucleus basalis decreased attention & intellect (AD, PD)
http://www.hermes-press.com/Perennial_Tradition/hippocampus.gif
Hippocampus
Memory formation
HM: temporal lobes removed for intractable epilepsy no longer formed new memories
http://www.umassmed.edu/bnri/graphics/crusiofig1.gif
important for motivated & emotional behaviors (eating, drinking, sexual activity, aggressive behavior)
Limbic System
Ventricles
http://mywebpages.comcast.net/epollak/PSY255_pix/ventricles.PNG
Contain cerebrospinal fluid (CSF)
CSF reabsorbed into blood vessels, so continuous turnover
Protective
Reservoir for hormones, nutrients
Ventricle size can indicate problems
• Enlarged ventricles as in Alzheimer’s patients (cell loss).
• Lack of ventricles due to tumors etc.
Cortex• 2 hemispheres
– Communicate via corpus callosum & anterior commisure
• 4 lobes
http://pegasus.cc.ucf.edu/~Brainmd1/brmodelc.gif
http://www.urmc.rochester.edu/neuroslides/slides/slide201.jpghttp://trc.ucdavis.edu/mjguinan/apc100/modules/Nervous/grosscns/images/brain10.jpg
6 laminae (layers of cells)
The lobes of the cortex• Frontal
– Thinking– Prefrontal cortex
• Planning• Working memory• Socially appropriate
behavior• Delayed-response
task • Lobotomies
– Primary motor cortex
• Broca’s aphasia
The lobes of the cortex
• Parietal– Sensing
• Primary sensory cortex
Homunculus
The lobes of the cortex• Temporal
– Spoken language comprehension
• Wernike’s aphasia
– Hearing– Vision
• Movement perception
• Face recognition
– Emotional motivational behavior
The lobes of the cortex
• Occipital – Vision
• Primary visual cortex
• Damage causes “cortical blindness”
Functions
• Forebrain– the cool stuff (thinking, perceiving, big part of emotion)
• Midbrain– sensory pathways
• Hindbrain– motor control, reflexes (breathing, heart rate, etc)
Sensory Organs
Sensory Function and Vision…
The General Senses…
• Sensory receptors – specialized cells that monitor the environment
and relay information to the CNS.– Free nerve endings are the simplest type:
they are the dendrites of sensory neurons– Complex receptors (eyes) are housed in
organs– Some receptors respond to only one kind of
stimulus
All sensory receptors send info to the CNS via an action potential…
• At the CNS, info is routed according to the stimulus and its location
• The stronger the stimulus, the higher the frequency of action potentials
• Some receptors adapt, that is their sensitivity to a stimulus is reduced if the stimulus is continually applied (smell)– The RAS can heighten or reduce awareness
of sensory information
General versus special senses…
• General sense receptors included those for temperature, pain, pressure, touch, vibration & proprioception (body position)
• These receptors are very simple in nature
“Special” senses• Special senses
monitor vision, hearing, olfaction, gustation, and equilibrium through specialized sense organs
• These sense organs are highly specialized
Tactile receptors…• May be simple or complex,
superficial or deep, fine (provide detailed information) or crude (provide little information)
• Merkel’s – fine touch and pressure
• Pacinian – deep pressure• Meissner’s – fine touch
and pressure in select areas
• Ruffini – pressure or distortion in deep dermal layers
The olfactory organs…
Gustation….taste
• http://www.bbc.co.uk/science/humanbody/body/factfiles/taste/taste_ani_f5.swf
• Taste buds are organs containing gustatory & supporting cells that lie within papillae
• Chemicals contact taste hairs which change the MP of taste cells & leads to an AP in the sensory neuron
• 4 primary taste sensations – sweet, salt, sour, bitter
• Sensory Pathway: sensory receptors>medulla> thalamus>primary sensory cortex
A complex sensory organ: the eye.
• is surrounded by accessory structures that act to protect, lubricate, and support it
• is a light, compact, durable, and highly specialized hollow organ that weighs about 8 oz and measures 1 inch in diameter.
• is divided into anterior (aqueous) & posterior (vitreous) cavities.
• its walls are made of 3 “tunics”
Accessory structures of the eye…• eyelids (palpebrae)• eyelashes & brows• exocrine glands• lacrimal apparatus• Conjunctiva• 6 extrinsic occulomotor
muscles:– the inferior, superior, lateral
and medial rectus muscles – the superior and inferior
oblique muscles
Eye anatomy…..
• http://www.macula.org/anatomy/eyeframe.html
• The hollow eye is divided into 2 cavities:
• An anterior cavity which contains aqueous humor
• A posterior cavity which holds vitreous humor
• Humors act to stabilize eye shape and provide nutrients
The Tunics of the eye…
• Fibrous - the sclera & anterior cornea
• Vascular – contains blood vessels, lymphatics, choroid & intrinsic muscles of the iris &ciliary bodies (they support the lens)
• Neural – the retina, it contains the rods and cones (photoreceptor cells), bipolar &ganglion cells
Retinal organization …• The retina is made of several cell layers:
– Photoreceptor cells – rods lie along the periphery & cones lie at the back of the retina
– Bipolar cells synapse with the rods and cones– Ganglion cells synapse with the bipolar cells– The axons of the ganglion cells form the optic
nerve– http://www.macula.org/anatomy/retinaframe.html
http://www.macula.org/anatomy/anatomy.html
• Macula lutea – area on the retina where the visual image forms, it contains only cones with the greatest numbers at the fovea centralis
• Optic Disc or “blind spot” is the area where the ganglion cell axons exit the eye to form the optic nerve