the brain

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