Nervous System, Senses, and Endocrine System

Avian brain

Contains three divisions: forebrain, midbrain, and hindbrain

Nervous system

Integrates and controls various functions in the body; obtains environmental information, analyzes/responds to information obtained via sensory receptors, stores information as memory and learning, and coordinates outgoing motor impulses to skeletal muscles and the viscera (smooth muscle, cardiac muscle, and glands)

Central nervous system (CNS)

Brain and spinal cord; protected by skull and vertebral column

Peripheral nervous system (PNS)

Comprises of cranial and spinal nerves that originate from the brain/spinal cord, the autonomic nervous system, ganglia, and the sensory organs

Forebrain

Consists of the cerebral hemispheres, olfactory lobes, hypothalamus, and pituitary gland; functions in integration, instinctive behavior, and intellegence

Midbrain

Mainly consists of optic lobes; functions in vision, muscular coordination, and physiological control (homeostasis)

Hindbrain

Consists mainly of the cerebellum and medulla oblongata; functions in brain/spinal cord linkage and the peripheral nervous system

Sensory organs

organs that recieve various stimuli from the bird’s environment; depending on the mode of action of the stimuli, special endings on the nerves will perveive that stimulus; includes the eyes, ears, nose, and taste buds

Eyes

The most important organ of birds; vision is the most important sensory output for birds; commonly very large; vary in shape (globular, flattened, or tubular)

Globular eyes

Eyeshape of diurnal birds; require high resolution to see over great distances (hawks, etc.)

Flattened eyes

Eyeshape of most birds

Tubular eyes

Eyeshape of nocturnal birds; allows increased accommodation (focusing) and light-gathering

Eye comparison

Ears

Divided into three regions: the outer ear, middle ear, and inner ear

Middle ear

Portion of the ear separated from the outer ear by the tympanic membrain (eardrum); contains only one bone (columella); transmits sound vibrations from tympanum to inner ear

Inner ear

Portion of the ear consisting of the cochlea and the three semicircular ducts; functions in both hearing and equilibrium

Olfactory organ

Olfactory lobes are generally small in birds; birds have a mediocre sense of smell

Taste buds

Organ located at the base of the tongue and mouth floor; contain nerve endings from the glossopharyngeal nerve; small quantaties of taste chemicals are actually recognized by the brain receptors

Mechanoreception

Sense of touch; birds process touch, pressure, temperature, and pain receptors; birds may sense barometric pressure (sense oncoming storms and modify foraging behavior or altitude accordingly)

Endocrine system

Birds have common glands to produce, store, and secrete hormones